Fuel Line Sizing Calculator
Size fuel line by HP, length, and -AN fitting — keeps pressure drop and velocity under safe limits.
How to Use
- Enter HP, BSFC, line length, and candidate -AN size.
- Tool reports pressure drop and velocity — target < 3 psi and < 5 ft/s.
Demand + line
Pressure drop
Formula
Flow velocity
v = Q / A
Darcy-Weisbach
ΔP = f · (L/D) · (ρ · v² / 2)
Fitting loss
ΔP_fit ≈ K · (ρ · v² / 2), K ≈ 0.6 per bend
Frequently Asked Questions
-AN vs NPT?
-AN is SAE dash sizes. -6 ≈ 3/8" ID, -8 ≈ 1/2", -10 ≈ 5/8". Stick to -AN for flow calcs — NPT taper bores vary.
Why not go huge on line size?
Bigger line = more fuel sloshing, more weight, slower pressure response at throttle tip-in. Match it, don't over-size.
Supply vs return?
Supply is critical (pressure). Return can be one size smaller if pressure relief is set properly — but don't undersize on high-HP returnless.
Common Use Cases
Turbo build plumbing
Pick -6 vs -8 before buying hose and fittings.
Long-chassis truck
Tank-to-rail runs over 15 ft need careful sizing.
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