Air Line Sizing Calculator
Air loses pressure on its way down a hose, and it loses it fastest in a long, skinny one. Put in what your tool needs and how far the air has to travel, and this estimates the pressure your tool actually sees and tells you whether to go up a hose size.
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Pressure drop per 50 ft of hose, 90 PSI in
| Flow | 1/4" hose | 3/8" hose | 1/2" hose |
|---|---|---|---|
| 2 CFM (nailer) | about 3 PSI | under 1 PSI | under 1 PSI |
| 5 CFM (1/2" impact) | about 17 PSI | about 2 PSI | under 1 PSI |
| 8 CFM (DA sander) | about 40 PSI | about 5 PSI | about 1 PSI |
| 10 CFM (paint gun) | starves | about 8 PSI | about 2 PSI |
Estimates from the standard pressure-drop relationship for compressed air in smooth hose; real numbers vary with hose material, fittings and temperature. Each quick coupler costs roughly 1 to 3 PSI at impact-wrench flow, so count them.
How to size it without the math
- Nailers only: 1/4" is fine to 100 ft. They use a puff of air, not a flow.
- Anything that spins: 3/8" minimum. Impact wrenches, ratchets, grinders, cutoff tools.
- Over 50 ft or 8+ CFM: 1/2". Sanders, paint guns, sandblasting, long runs.
- Shop piping: 3/4" main line, 1/2" drops, and keep the flexible hose short at the end.
- Couplers add up. A 1/4" body coupler is the narrowest point in a 3/8" line. If you are chasing the last few PSI, use 3/8" body couplers (Foster 4 Series) on 3/8" hose.
Related on Industrial Supply World
- Air hose sizing: 1/4" vs 3/8", and which material to buy
- Best air compressors for a home garage
- Air coupler interchange finder
- Build your own air hose, cut to length with the ends you want
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