--- title: What Size AN Fitting Do I Need? A Complete Guide to Measuring AN Fittings, Hoses, and Pipes description: A clear guide to AN fitting, hose, and tube sizes—so you always get the right dimensions for your motorsport or custom parts setup. (≤200 characters) --- [Skip to content](https://info.speedingparts.eu/how-do-you-measure-an-fittings-hoses-and-pipes-correctly-#main-content) [![Speeding\_Logo\_black\_Byline\_pp-2](https://info.speedingparts.eu/hs-fs/hubfs/Speeding_Logo_black_Byline_pp-2.png?width=200&height=60&name=Speeding_Logo_black_Byline_pp-2.png)](https://www.speedingparts.eu) Open main navigation Close main navigation How can we help you? - There are no suggestions because the search field is empty. 1. [Speeding Support](https://info.speedingparts.eu/?hsLang=en) 2. [Hose and Fittings](https://info.speedingparts.eu/hose-and-fittings?hsLang=en) # What Size AN Fitting Do I Need? A Complete Guide to Measuring AN Fittings, Hoses, and Pipes ## Learn how to correctly measure AN fittings, hoses, and pipes — avoid common sizing mistakes and choose the right parts for your motorsport or custom build. #### AN-fittings measurement - A guide to the right size ![](https://www.speedingparts.com/image/23572/AN-fittings-measurements-information.jpg) Dimensions of AN fittings, hose and pipes are some of the most common questions and misconceptions that exist about the AN system. AN is measured in inches where AN1 in theory is 1/16", AN8 is then 1/2" and AN16 is thus 1". AN8 is not 10 or 8mm which is a common misconception. How to measure is also a common misunderstanding when there are different types of AN fittings, hose, pipes and key grips. And you get different values for all of these measurements. To make it clear, we have divided the information into different categories: 1. **AN-fitting measurements** 2. **AN-hose measurements** 3. **AN-pipe / tube measurements** 4. **AN-key grip measurements** Do you measure outer diameter or inner diameter? Thread inside or outside diameter? We'll cover how to do this right here! **AN fittings are an abbreviation of Army-Navy and came during the Second World War when lighter and better tolerance fittings than ordinary hydraulic once was needed. AN fittings have become a kind of standard in the aftermarket, performance and hobby aviation.**       ### 1. AN-fitting measurements AN fittings are simply explained as a JIC fitting in aluminum with higher tolerances. AN fitting size is measured over the thread.     **AN-fitting male (outer diameter)** Below, the thread is presented in inches / metric dimensions in the thread / metric outer diameter. **AN4** = 7/16" -20 = ~9,1mm in threads = ~11,8mm OD **AN6** = 9/16" -18 = ~11,6mm in threads = ~14,2mm OD **AN8** = 3/4" -16 = ~16,6mm in threads = ~ 19,0mm OD **AN10** = 7/8" -14 = ~19,5mm in threads = ~22,3mm OD **AN12** = 1-1/16" -12 = ~23,8mm in threads = ~26,9mm OD **AN16** = 1-5/16" -12 = ~30,2mm in threads = ~33,3mm OD **AN20** = 1-5/8" -12 = ~38,2mm n threads = ~41,4mm OD ![](https://www.speedingparts.com/image/23576/thread-outer-diameter-an-fitting-male.jpg)     **AN-fitting female (inside diameter)** Here, the thread is presented in inches / metric inner diameter. **AN4** = 7/16" -20 = ~9,9mm ID **AN6** = 9/16" -18 = ~12,9mm ID **AN8** = 3/4" -16 = ~17,5mm ID **AN10** = 7/8" -14 = ~20,6mm ID **AN12** = 1-1/16" -12 = ~24,9mm ID **AN16** = 1-5/16" -12 = ~31,2mm ID **AN20** = 1-5/8" -12 = ~39,1mm ID ![](https://www.speedingparts.com/image/23577/thread-inner-diameter-an-fitting-female.jpg)     **AN-hose end inner diameter** An approximate internal dimension of AN hose ends is presented here. Note that the internal dimensions of hose ends and fittings may differ depending on the type, material manufacturer, etc. Therefore, these internal measurements should only be used as guidelines. **AN4** = ~3,7mm **AN6** = ~6,0mm **AN8** = ~8,6mm **AN10** = ~11,1mm **AN12** = ~14,3mm **AN16** = ~19mm **AN20** = ~25mm Corresponding AN adapters generally have a 1 mm larger inner diameter. Should an adapter be reduced to a smaller thread, the inner diameter will also shrink. ![](https://www.speedingparts.com/image/23579/an-fittings-inner-diameter-measurement.jpg)       ### 2. AN-hose measurements AN hose size is measured inside the hose = (inner diameter of the hose). Depending on hose type, the outer diameter of the hose will vary. The type of hose technology has also changed since the Second World War when these connections came so the actual dimensions of the AN hose can vary. It also differs between manufacturers sometimes. So be sure to use the right hose for your AN hose ends and AN-system!     **Braided rubber hose measurement (-1950)** **AN3** = 3/16" hose id = ~4,76mm **AN4** = 1/4" hose id = ~6,35mm **AN5** = 5/16" hose id = ~7,9mm **AN6** = 3/8" hose id = ~9,5mm **AN8** = 1/2" hose id = ~12,7mm **AN10** = 5/8" hose id = ~15,9mm **AN12** = 3/4" hose id = ~19,05mm **AN16** = 1" hose id = ~25,4mm **AN20** = 1-1/4" hose id = ~31,75mm **Braided rubber hose measurement (nowdays)** **AN4** = 7/32" ~5,4mm **AN5** = 5/16" ~7,9mm **AN6** = 11/32 ~8,7mm **AN8** = 7/16" ~11,1mm **AN10** = 9/16" ~14,2mm **AN12** = 11/16" ~17,4mm **AN16** = 7/8" ~22,2mm **AN20** = 1-1/8" ~28,5mm **Braided PTFE hose measurement (nowdays)** **AN4** = 3/16" ~4,8mm **AN6** = 21/64" ~8,1mm **AN8** = 27/64" ~10,7mm **AN10** = 33/64" ~13,0mm **AN12** = 41/64" ~16,3mm **AN16** = 7/8" ~22,2mm ![](https://www.speedingparts.com/image/23575/Hose-size-an-fittings.jpg)       ### 3. AN-pipe / tube measurements AN pipe size is measured on the pipe outer diameter. The thickness varies between manufacturers and therefore the inner dimension is different. But overall, an AN4 pipe has ~ 1.5mm wall thickness and an AN12 pipe ~ 2.5mm wall thickness.     **AN4** = 1/4" pipe OD = ~6,35mm **AN5** = 5/16" pipe OD = ~7,9mm **AN6** = 3/8" pipe OD = ~9,5mm **AN8** = 1/2" pipe OD = ~12,7mm **AN10** = 5/8" pipe OD = ~15,9mm **AN12** = 3/4" pipe OD = ~19,05mm ![](https://www.speedingparts.com/image/23574/Pipe-size-an-fittings.jpg)     ### 4. AN-key grip measurements The key grip on AN fittings is also measured in inches and since European sizes are metric (millimeters), an adjustable socket wrench or inch tools is recommended during assembly so you get the correct engagement. There are special tools just for AN fittings, but a standard adjustable wrench works great.     **AN3** = 1/2" = ~12,7mm **AN4** = 9/16" = ~14,3mm **AN6** = 11/16" = ~17,48mm **AN8** = 7/8" = ~22,23mm **AN10** = 1" = ~25,4mm **AN12** = 1-1/4" = ~31,75mm **AN16** = 1-1/2" = ~38,1mm **AN20** = 1-13/16" = ~46,0mm ![](https://www.speedingparts.com/image/23573/Key-grip-size-an-fittings.jpg)   - [Hose and Fittings](https://info.speedingparts.eu/hose-and-fittings?hsLang=en) - [Engine](https://info.speedingparts.eu/engine?hsLang=en) - [Fuel System](https://info.speedingparts.eu/fuel-system?hsLang=en) - [Brake system](https://info.speedingparts.eu/brake-system?hsLang=en) - [Chassis](https://info.speedingparts.eu/chassis?hsLang=en) - [Powertrain](https://info.speedingparts.eu/powertrain?hsLang=en) - [Electrical](https://info.speedingparts.eu/electrical?hsLang=en) - [Turbo](https://info.speedingparts.eu/turbo?hsLang=en) [![Speeding\_Logo\_black\_Byline\_pp-2](https://info.speedingparts.eu/hs-fs/hubfs/Speeding_Logo_black_Byline_pp-2.png?width=200&height=60&name=Speeding_Logo_black_Byline_pp-2.png "Speeding_Logo_black_Byline_pp-2")](https://www.speedingparts.eu) Copyright © 2026, Speeding AB