What Does Air Hose Size Mean? Inside Diameter, Outside Diameter, and Dash Size<\/h2>\n\n\n\n
Air hose dimensions come in three values people routinely confuse: the inside diameter, the outer diameter, and the dash size. The air hose size is always the inside diameter \u2014 the bore that carries compressed air. The outer diameter is the same bore plus two wall thicknesses, so it is always larger and varies with the rubber, PVC, or polyurethane construction. The dash size is a shortcut number that expresses the same inside diameter in sixteenths of an inch.<\/p>\n\n\n\n Figure 1. The inside diameter defines the size; the outer diameter is the bore plus two wall thicknesses.<\/p>\n\n\n\n Two rules of thumb keep this straight: the ID is always smaller than the OD \u2014 by two wall thicknesses \u2014 and the OD column above holds for standard rubber hose. A dash number of -8 means the same 1\/2-inch bore in any construction: dash sizes describe the bore, so the air hose size stays the same whether the label reads 1\/2 in, 12.7 mm, or -8. When you are choosing among the three standard air hose sizes, our what size air hose do i need guide walks through tool-by-tool recommendations.<\/p>\n\n\n\n Measuring an air hose takes one tool \u2014 a digital caliper \u2014 and two minutes at the bench. This is the method we use in the HENGHUA test shop for every incoming reel, and it answers the question we hear most: “My compressor sits 60 feet from the bench \u2014 which hose should I run?” The answer starts with the bore.<\/p>\n\n\n\n Figure 2. Measure the open bore across two points and average the readings \u2014 coiled hose is rarely perfectly round.<\/p>\n\n\n\n A note on used hose: new 3\/8-inch hose reads 9.4\u20139.6 mm on the bore. Our factory records show the bore grows about 0.1\u20130.3 mm after roughly two years of service, as reinforcement and cover wear relax the wall \u2014 so a reading above 9.6 mm on used hose suggests service growth, and it is a sign to check flow and replace the line.<\/p>\n\n\n\n In our shop tests across five production lots, 3\/8-inch rubber hose measured 9.4\u20139.6 mm on the bore and 15.8\u201316.0 mm outside, matching the 9.53 mm ID \/ 5\/8 inch OD standard within molding tolerance. If your reading lands between two sizes, choose the larger one \u2014 the larger bore flows more air, and an oversized bore only costs a little extra.<\/p>\n\n\n\n The air hose outer diameter is what fittings, clamps, ferrules, and reels actually touch, so it matters for mechanical fit, while the bore defines the air hose size. Measure it with the caliper’s outside jaws at two points 90 degrees apart, away from any seam or printing that would skew the reading, then calculate wall thickness as (OD \u2212 ID) \u00f7 2.<\/p>\n\n\n\n Wall thickness explains why two hoses with the same ID look different: a heavy rubber hose rated for 300 PSI has roughly a 1\/8-inch (3.2 mm) wall, while a lightweight polyurethane recoil hose runs about half that \u2014 1\/16 to 3\/32 inch. The table below lists typical values.<\/p>\n\n\n\n When ordering, always specify both the ID and the OD \u2014 a 5\/8-inch OD can mean a 3\/8-inch ID rubber hose or a 1\/2-inch ID thin-wall hose, two completely different air hose outer diameter specifications. Pair the OD with an ID measurement or the printed bore. Wall thickness also decides which air hose fittings grip correctly: push-on fittings and clamps need a wall thick enough to hold.<\/p>\n\n\n\n A dash size is the inside diameter counted in sixteenths of an inch, written with a minus sign: -4, -6, -8, and so on. The conversion is a single multiplication \u2014 dash = ID in inches \u00d7 16. A 1\/4-inch bore is 4\/16, hence -4; a 3\/8-inch bore is 6\/16, hence -6. The dash numbering system comes from SAE J514 hydraulic fitting standards \u2014 each dash equals 1\/16 inch.<\/p>\n\n\n\n Figure 3. Dash number to inch to millimeter: -4 = 1\/4 in = 6.35 mm, -6 = 3\/8 in = 9.53 mm, -8 = 1\/2 in = 12.7 mm.<\/p>\n\n\n\n Dash sizes appear wherever hose is specified by number rather than by fraction \u2014 most often on DOT air brake hose built to SAE J1402 (the construction standard behind U.S. DOT FMVSS 106 \u2014 the air brake hose size on trucks is commonly -6 or -8), on hydraulic hose with JIC fittings (Joint Industry Council 37\u00b0 flare, per SAE J514) or ORFS fittings (O-Ring Face Seal, per SAE J1453), and on many OEM drawings. If a spec sheet says “1\/2-inch hose, -8,” both names describe the same bore; the air hose dash size simply replaces the fraction with a number you can check on the label.<\/p>\n\n\n\n A -6 and a 10 mm label are close but separate bores (9.53 mm vs 10.0 mm) \u2014 the caliper reading tells you which one you have. This distinction matters for OEM drawings and export orders, where one decimal place in the bore spec decides the fitting family.<\/p>\n\n\n\n If you buy hose for the EU market, metric bores \u2014 6 mm, 8 mm, 10 mm, and 13 mm \u2014 are the naming convention, and the method for how to measure air hose size is identical: caliper across the open bore. The conversion trap: an 8 mm bore is 5\/16 inch, and treating it as 3\/8 inch is the most common metric mix-up on this topic.<\/p>\n\n\n\n Two practical notes: measure in millimeters and compare against 6.35 mm, 9.53 mm, and 12.7 mm \u2014 fraction conversion adds a step where errors creep in; and check the label for OD. On polyurethane recoil tubes the printed size is sometimes the outer diameter (8 mm OD and 10 mm OD tubes are common), so confirm which dimension the label states before ordering. HENGHUA supplies both metric- and inch-labeled air hoses, so the same reel can be specified either way.<\/p>\n\n\n\n The air hose fitting size is a separate measurement from the hose bore, and mismatches here cause more field failures than the hose itself. Two things need measuring:<\/p>\n\n\n\n For NPT threads (the standard on air hose per ANSI B1.20.1 \u2014 see our NPT vs BSP threads guide for the metric alternative), measure the outside diameter of the male thread at its widest point with the caliper jaws. A 1\/4-inch NPT thread measures about 0.54 in (13.7 mm) across the crests; 3\/8-inch NPT measures about 0.68 in (17.1 mm); 1\/2-inch NPT about 0.84 in (21.3 mm). Measure the male thread the female end mates with, then confirm the fit before assembly.<\/p>\n\n\n\n Quick-connect couplers are sized by body, and the two common air hose fitting size families are 1\/4 inch (most workshops) and 3\/8 inch (high flow). Use only matching plug profiles: I\/M (Industrial\/Military) plugs fit I\/M couplers, and A (Automotive) plugs fit A couplers. To identify a plug with a caliper, measure the widest point of its outer profile \u2014 our shop measurements put A-type plugs at about 0.31 in and I\/M-type at about 0.32 in \u2014 and the profile width is the dimension that tells the two families apart. Our quick-connect couplers page shows the profiles side by side. The fitting bore should be at least as large as the hose bore: at 90 PSI inlet, a 1\/4-inch bore hose through a coupler with a 1\/8-inch internal bore delivers roughly 12 SCFM, where a matching 1\/4-inch-bore coupler passes about 20 SCFM (experience values from our test bench). A reducing bushing adapts a larger coupler to a smaller tool inlet only; for a larger tool, use a full-size coupler.<\/p>\n\n\n\n The chart below combines every measurement from this guide into one selection table for the standard air hose sizes. To read it, start with your tool’s SCFM demand at 90 PSI, find the matching air hose size row, then check the dash number and comfortable run length against what your fittings and reels accept.<\/p>\n\n\n\n Airflow values are typical tool demand at 90 PSI inlet (industry experience values) \u2014 the hose itself passes more, and a 1\/4-inch bore with a matching coupler flows roughly 20 SCFM. Max comfortable run assumes typical tool demand with roughly \u226410% pressure drop. Typical OD by construction \u2014 see the size table above.<\/em><\/p>\n\n\n\n Figure 4. The same bore can be named three ways: a fraction of an inch, a metric value, or a dash number. The image summarizes the main sizes; the size table above is the full reference.<\/p>\n\n\n\n Pressure drop is the hidden cost of a wrong reading: in our shop tests at 90 PSI inlet and 20 SCFM flow, a 50-foot run of 1\/4-inch hose loses 6\u20138 PSI, while 1\/2-inch hose over the same run loses about 1 PSI under the same conditions \u2014 enough to starve tools rated above 15 SCFM. When in doubt, choose the larger bore for flow and the larger dash number for fittings.<\/p>\n\n\n\n Material changes how the size reads in practice \u2014 rubber, PVC, or polyurethane each handle pressure, cold, and kinking differently \u2014 so our rubber vs PVC air hose comparison is worth a read before you commit to one construction.<\/p>\n\n\n\n Not sure which bore your tool line needs? Browse the HENGHUA air compressor hoses range, then send your tool list and longest run to our engineering team for a confirmed specification within one business day.<\/p>\n\n\n\n The most expensive mistake is the quiet one: a hose that fits the coupler but is one size too small for the tool. It runs, so nothing is flagged, and the tool performs below rating until someone measures the bore \u2014 a caliper reading takes less time than replacing a starved tool.<\/p>\n\n\n\n By inside diameter \u2014 the air hose inside diameter is the dimension that defines the size, and the OD is always larger by two wall thicknesses. If a seller quotes a size without saying “ID” or “inside diameter,” the convention is the bore \u2014 for lightweight recoil hoses, confirm with a caliper, since some are labeled by OD.<\/p>\n\n\n\n Read the markings printed on the cover, then confirm with a digital caliper across the open bore. Match your air hose inside diameter reading to the nearest standard size (6.35 mm = 1\/4 inch, 9.53 mm = 3\/8 inch, 12.7 mm = 1\/2 inch), then multiply the inch value by 16 for the dash size.<\/p>\n\n\n\n Wrap a tape measure around the hose and divide the circumference by 3.14 for the OD, or insert drill bits into the bore until one fits snugly for the ID. A 1\/2-inch OD rubber hose wraps to about 1.57 inches. These methods are accurate to roughly 1\/32 inch \u2014 use them for identification, and use a caliper for fitting-critical measurements.<\/p>\n\n\n\n An air hose dash size of -6 is 6\/16 of an inch, or 3\/8 inch (9.53 mm) inside diameter. The dash number divided by 16 gives the bore in inches: -4 is 1\/4 inch, -8 is 1\/2 inch, -12 is 3\/4 inch, and -16 is 1 inch.<\/p>\n\n\n\n Yes \u2014 the bore controls how much airflow reaches the tool at usable pressure. An undersized hose starves high-flow tools and adds pressure drop over long runs; an oversized hose costs and weighs more. The right bore matches the tool’s SCFM demand and run length.<\/p>\n\n\n\n Start from three numbers: your most demanding tool’s SCFM demand at 90 PSI, the longest run to it, and how many tools draw air at once. 3\/8 inch is the safe default for most workshops \u2014 it clears impact wrenches, framing nailers, and ratchets on runs up to 50 ft. Step up to 1\/2 inch when the run goes beyond 50 ft, several tools run at once, or the compressor output exceeds roughly 20 SCFM; drop to 1\/4 inch for short, light-duty lines. Match the fitting bore to the hose bore so the connection keeps full flow, and see our air hose selection guide for tool-by-tool detail.<\/p>\n\n\n\n Use 3\/8 inch (-6) for impact wrenches up to 1\/2-inch drive. An impact wrench draws roughly 4\u20136 SCFM at 90 PSI, well inside what 3\/8-inch hose delivers over 50 ft (10\u201320 SCFM), and 1\/4-inch hose handles light 3\/8-inch-drive wrenches on short 25 ft runs. Keep the coupler bore at least equal to the hose bore so the fitting holds the flow.<\/p>\n\n\n\n Measure the male NPT thread outer diameter at its widest point: 1\/4-in NPT reads about 0.54 in (13.7 mm), 3\/8-in NPT about 0.68 in (17.1 mm), and 1\/2-in NPT about 0.84 in (21.3 mm). For quick-connect couplers, measure the plug’s outer profile at the widest point \u2014 A (Automotive) plugs read about 0.31 in and I\/M (Industrial\/Military) plugs about 0.32 in. Then match the coupler sizes \u2014 the body (1\/4 in or 3\/8 in) \u2014 to the hose bore.<\/p>\n\n\n\n HVLP spray guns are flow-hungry \u2014 most models draw 6\u201312 SCFM at 40 PSI at the gun \u2014 so use 3\/8-inch (-6) hose for runs up to 50 ft and 1\/2-inch (-8) for longer runs or production finishing. The larger bore keeps the pressure stable so the finish stays consistent.<\/p>\n\n\n\n The cover printing usually reads bore, working pressure, and temperature range, for example “3\/8 in (9.53 mm) 300 PSI W.P.” The first number is the air hose size \u2014 the inside diameter in inches or mm \u2014 and W.P. means working pressure. On used hose, our factory records show bores can grow 0.1\u20130.3 mm after roughly two years of service, so verify with a caliper when the print is worn or the hose is old.<\/p>\n\n\n\n 8 mm is labeled 5\/16 inch (0.315 in), and 10 mm (0.394 in) sits between 3\/8 inch (9.53 mm) and 7\/16 inch. Treat metric hose as its own size: measure the bore in millimeters and match fittings to the same metric bore \u2014 an 8 mm or 10 mm hose pairs with metric couplers directly, or with inch couplers through a reducer.<\/p>\n\n\n\n DOT air brake hose is built to SAE J1402, the construction standard behind U.S. DOT FMVSS 106, and the two common sizes are -6 (3\/8 in, 9.53 mm) and -8 (1\/2 in, 12.7 mm). Verify the size with a caliper across the open bore, then confirm the cover printing shows SAE J1402 and the same dash or inch size. When replacing a line, match both the bore and the end fitting type so the new hose carries the same airflow and pressure rating as the original.<\/p>\n\n\n\n State the bore in inches and millimeters plus the dash number \u2014 for example “3\/8 in (9.53 mm), -6” \u2014 then add the working pressure, temperature range, and fitting standard (NPT per ANSI B1.20.1, or a metric thread). Note the naming system, because SAE and ISO conventions label the same bore differently (see the dash and metric tables above); a drawing that states all three names reads the same in any market.<\/p>\n\n\n\n Measuring an air hose is a four-step habit: read the printed markings, confirm the air hose size on the bore with a caliper, convert it to the dash number if your fittings use dash sizes, and match the NPT threads and couplers to that bore. OD and wall thickness matter for mechanical fit, and the common mistakes above \u2014 OD-as-size, ferrule readings, metric mixing \u2014 are all avoidable with one caliper and two minutes. If you are sourcing air hoses for a retail line, distribution, or OEM program, send your required bore sizes, lengths, and fitting types to the HENGHUA engineering team \u2014 we will confirm the correct specification, provide samples and technical documentation, and quote bulk pricing with factory lead times before you commit to an order. Contact our engineering team.<\/p>\n\n\n\n HENGHUA is a professional reinforced air hose manufacturer of rubber air hoses and hose assemblies, supplying workshops, distributors, and OEM brands worldwide. Every size in this guide \u2014 1\/4, 3\/8, 1\/2, 5\/8, 3\/4, and 1 inch bore \u2014 is a standard production size in our plant, so the ID, OD, wall thickness, and dash size conversions described here match what we actually ship. Each reel is bore-checked with calibrated gauges and pressure-tested before packing, with factory-crimped brass fittings, custom lengths, and OEM branding as standard options \u2014 the inside diameter printed on the cover is the value you can design around, the same number you will measure with the caliper method above.<\/p>\n\n\n\n Figure 5. HENGHUA reinforced air hoses \u2014 the bore printed on the cover is the value this guide teaches you to verify.<\/p>","protected":false},"excerpt":{"rendered":" Cover. Measure the open bore with a caliper \u2014 the air hose size is the inside diameter. Air hose size is the inside diameter (ID) of the bore \u2014 the passage compressed air actually flows through \u2014 always expressed by the bore, in fractions of an inch or in dash sizes. Quick answer: measure the open bore […]<\/p>\n","protected":false},"author":1,"featured_media":3796,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_surecart_dashboard_logo_width":"180px","_surecart_dashboard_show_logo":true,"_surecart_dashboard_navigation_orders":true,"_surecart_dashboard_navigation_invoices":true,"_surecart_dashboard_navigation_subscriptions":true,"_surecart_dashboard_navigation_downloads":true,"_surecart_dashboard_navigation_billing":true,"_surecart_dashboard_navigation_account":true,"site-sidebar-layout":"default","site-content-layout":"","ast-site-content-layout":"default","site-content-style":"default","site-sidebar-style":"default","ast-global-header-display":"","ast-banner-title-visibility":"","ast-main-header-display":"","ast-hfb-above-header-display":"","ast-hfb-below-header-display":"","ast-hfb-mobile-header-display":"","site-post-title":"","ast-breadcrumbs-content":"","ast-featured-img":"","footer-sml-layout":"","ast-disable-related-posts":"","theme-transparent-header-meta":"","adv-header-id-meta":"","stick-header-meta":"","header-above-stick-meta":"","header-main-stick-meta":"","header-below-stick-meta":"","astra-migrate-meta-layouts":"set","ast-page-background-enabled":"default","ast-page-background-meta":{"desktop":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"tablet":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"mobile":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""}},"ast-content-background-meta":{"desktop":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"tablet":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"mobile":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""}},"footnotes":""},"categories":[1],"tags":[798,801,800,799,797],"class_list":["post-3795","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-blog","tag-air-hose-dash-size","tag-air-hose-fitting-size","tag-air-hose-inner-diameter","tag-air-hose-outer-diameter","tag-how-to-measure-air-hose-size"],"yoast_head":"\n![\"Cross-section](\"https:\/\/www.henghuahose.com\/wp-content\/uploads\/2026\/08\/air-hose-id-od-cross-section.jpg\")
<\/figure>\n\n\n\nAir Hose Size (ID)<\/th> Metric Equivalent<\/th> Dash Size<\/th> Typical OD (Rubber)<\/th> Typical Use<\/th><\/tr><\/thead> 1\/4 inch<\/td> 6.35 mm<\/td> -4<\/td> 1\/2 inch<\/td> Brad nailers, tire inflators, blow guns<\/td><\/tr> 3\/8 inch<\/td> 9.53 mm<\/td> -6<\/td> 5\/8 inch<\/td> Most workshop tools, impact wrenches<\/td><\/tr> 1\/2 inch<\/td> 12.7 mm<\/td> -8<\/td> 3\/4 inch<\/td> Spray guns, sandblasters, high-flow tools<\/td><\/tr> 5\/8 inch<\/td> 15.9 mm<\/td> -10<\/td> 7\/8 inch<\/td> Air brake lines, long distribution runs<\/td><\/tr> 3\/4 inch<\/td> 19.1 mm<\/td> -12<\/td> 1 inch<\/td> Shop mains, manifold supply<\/td><\/tr> 1 inch<\/td> 25.4 mm<\/td> -16<\/td> 1-1\/4 inch<\/td> Main header lines, high-volume systems<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n How to Measure Air Hose Size: 4 Steps at the Bench<\/h2>\n\n\n\n
\n
![\"Person](\"https:\/\/www.henghuahose.com\/wp-content\/uploads\/2026\/08\/air-hose-id-caliper-measurement.jpg\")
<\/figure>\n\n\n\nHow to Measure Air Hose Outer Diameter and Wall Thickness<\/h2>\n\n\n\n
Hose Construction<\/th> Typical Wall Thickness<\/th> 3\/8-Inch Hose Typical OD<\/th> Best For<\/th><\/tr><\/thead> Rubber with textile reinforcement<\/td> 1\/8 in (3.2 mm)<\/td> 5\/8 in (15.9 mm)<\/td> Workshops, cold weather, abrasion<\/td><\/tr> PVC<\/td> 1\/8\u20135\/32 in<\/td> 5\/8\u201311\/16 in<\/td> Budget-friendly general use<\/td><\/tr> Polyurethane recoil<\/td> 1\/16\u20133\/32 in<\/td> 1\/2 in<\/td> Garage use, kink resistance<\/td><\/tr> Braided hybrid rubber<\/td> 5\/32\u20133\/16 in<\/td> 11\/16\u20133\/4 in<\/td> High working pressure, fleet use<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n What Is Air Hose Dash Size and How Do You Convert It?<\/h2>\n\n\n\n
![\"Hose](\"https:\/\/www.henghuahose.com\/wp-content\/uploads\/2026\/08\/air-hose-size-measurement-chart.jpg\")
<\/figure>\n\n\n\nDash Size<\/th> Inches (ID)<\/th> Millimeters<\/th> Where You See It<\/th><\/tr><\/thead> -4<\/td> 1\/4<\/td> 6.35<\/td> Small air tools, gauge lines<\/td><\/tr> -5<\/td> 5\/16<\/td> 7.94<\/td> Metric 8 mm counterpart; rare on inch air hoses<\/td><\/tr> -6<\/td> 3\/8<\/td> 9.53<\/td> Air brake hose, most air tools<\/td><\/tr> -8<\/td> 1\/2<\/td> 12.7<\/td> High-flow tools, hydraulic return lines<\/td><\/tr> -10<\/td> 5\/8<\/td> 15.9<\/td> Trailer air brake lines<\/td><\/tr> -12<\/td> 3\/4<\/td> 19.1<\/td> Shop mains, hydraulic pressure lines<\/td><\/tr> -16<\/td> 1<\/td> 25.4<\/td> Header lines, large hydraulic hoses<\/td><\/tr> -20<\/td> 1-1\/4<\/td> 31.8<\/td> Industrial air distribution<\/td><\/tr> -24<\/td> 1-1\/2<\/td> 38.1<\/td> Compressor discharge piping<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n Naming System<\/th> Typical Label<\/th> Bore Example<\/th> Where It Applies<\/th><\/tr><\/thead> Inch\/dash (SAE convention, used on J1402 air brake hose)<\/td> 3\/8 in or -6<\/td> 9.53 mm<\/td> US air brake hose, US tool market<\/td><\/tr> ISO metric naming (per ISO 4397)<\/td> 10 mm<\/td> 10.0 mm<\/td> EU industrial hose and fittings<\/td><\/tr> Fractional inch<\/td> 3\/8 in<\/td> 9.53 mm<\/td> US workshop hose<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n Metric Air Hose Sizes: 6 mm, 8 mm, 10 mm, and 13 mm<\/h2>\n\n\n\n
Metric Bore<\/th> Inch Equivalent<\/th> Nearest Dash<\/th> What It Is For<\/th><\/tr><\/thead> 6 mm<\/td> 0.236 in<\/td> -4 (6.35 mm)<\/td> Gauge lines, light tools<\/td><\/tr> 8 mm<\/td> 0.315 in (5\/16 in)<\/td> -5 (5\/16 in)<\/td> EU workshop hose \u2014 8.0 mm is 0.06 mm larger than the -5 dash bore, so treat it as its own size<\/td><\/tr> 10 mm<\/td> 0.394 in<\/td> -6 (9.53 mm)<\/td> EU workshop hose, close to 3\/8 in<\/td><\/tr> 13 mm<\/td> 0.512 in<\/td> -8 (12.7 mm)<\/td> EU high-flow hose, close to 1\/2 in<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n How to Measure Air Hose Fitting Size: Threads and Couplers<\/h2>\n\n\n\n
\n
Nominal Thread Size<\/th> Measured Thread OD (Male)<\/th> Threads per Inch<\/th> Common Location<\/th><\/tr><\/thead> 1\/4 in NPT<\/td> 0.54 in (13.7 mm)<\/td> 18<\/td> Most pneumatic tool inlets<\/td><\/tr> 3\/8 in NPT<\/td> 0.68 in (17.1 mm)<\/td> 18<\/td> High-flow hoses, regulators<\/td><\/tr> 1\/2 in NPT<\/td> 0.84 in (21.3 mm)<\/td> 14<\/td> Mains, large couplers<\/td><\/tr> 3\/4 in NPT<\/td> 1.05 in (26.7 mm)<\/td> 14<\/td> Headers, filter\/regulator sets<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n Air Hose Size Chart: ID, OD & Dash Sizes at a Glance<\/h2>\n\n\n\n
Air Hose Size (ID)<\/th> Dash Size<\/th> Typical Tool Demand (SCFM @ 90 PSI)<\/th> Max Comfortable Run<\/th> Best Tool Match<\/th><\/tr><\/thead> 1\/4 inch<\/td> -4<\/td> 5\u201310<\/td> 25 ft<\/td> Brad nailers, inflators, blow guns<\/td><\/tr> 3\/8 inch<\/td> -6<\/td> 10\u201320<\/td> 50 ft<\/td> Impact wrenches, ratchets, die grinders<\/td><\/tr> 1\/2 inch<\/td> -8<\/td> 20\u201335<\/td> 100 ft<\/td> HVLP spray guns, sandblasters<\/td><\/tr> 5\/8 inch<\/td> -10<\/td> 35\u201350<\/td> 150 ft<\/td> Air brake lines, distribution runs<\/td><\/tr> 3\/4 inch<\/td> -12<\/td> 50\u201375<\/td> 200 ft<\/td> Shop mains, manifold supply<\/td><\/tr> 1 inch<\/td> -16<\/td> 75\u2013100<\/td> 250 ft<\/td> Header lines, high-volume systems<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n ![\"Air](\"https:\/\/www.henghuahose.com\/wp-content\/uploads\/2026\/08\/air-hose-dash-size-conversion-chart.jpg\")
<\/figure>\n\n\n\nCommon Air Hose Measurement Mistakes<\/h2>\n\n\n\n
Mistake<\/th> Result<\/th> Fix<\/th><\/tr><\/thead> Measuring the outside diameter and calling it the size<\/td> A “1\/2-inch” hose that is actually 3\/8-inch bore<\/td> Always measure the open bore or check the printed ID<\/td><\/tr> Measuring across the brass ferrule or nipple<\/td> A reading that matches no standard size<\/td> Measure the hose body away from any fitting<\/td><\/tr> Measuring a coiled or kinked section<\/td> Oval reading, often 0.3\u20130.5 mm off<\/td> Straighten the hose and average two readings<\/td><\/tr> Mixing metric and imperial<\/td> An 8 mm bore treated as 3\/8 inch (it is 5\/16 inch)<\/td> Convert both to millimeters or both to inches<\/td><\/tr> Trusting worn or reprinted cover markings<\/td> Installing the wrong size, failing pressure tests<\/td> Verify with a caliper when the print is unclear<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n ![\"HENGHUA](\"https:\/\/www.henghuahose.com\/wp-content\/uploads\/2026\/08\/henghua-air-hose-product-3.jpg\")
<\/figure>\n\n\n\nFAQ: How to Measure Air Hose Size<\/h2>\n\n\n\n
Is air hose size measured by inside or outside diameter?<\/h3>\n\n\n\n
How do I know what size air hose I have?<\/h3>\n\n\n\n
How do you measure an air hose without a caliper?<\/h3>\n\n\n\n
What size is a -6 air hose?<\/h3>\n\n\n\n
Does air hose size matter?<\/h3>\n\n\n\n
What size air hose do I need?<\/h3>\n\n\n\n
I’m setting up a workshop with an impact wrench \u2014 what size air hose do I need to keep full torque?<\/h3>\n\n\n\n
How do I measure an air hose fitting or coupler size?<\/h3>\n\n\n\n
What is the air hose size for a HVLP spray gun?<\/h3>\n\n\n\n
How do I read the numbers printed on an air hose?<\/h3>\n\n\n\n
Are metric air hoses (8 mm, 10 mm) the same as 5\/16-inch and 3\/8-inch?<\/h3>\n\n\n\n
How do I verify the size of a DOT air brake hose on a trailer?<\/h3>\n\n\n\n
How do I specify air hose size on an OEM drawing?<\/h3>\n\n\n\n
Final Verdict: Measure the Bore, Then Choose the Fitting<\/h2>\n\n\n\n
About HENGHUA: Reinforced Air Hose Manufacturer<\/h3>\n\n\n\n