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Pipe Sizing Calculator

Size piping for water, steam, compressed air and gas in seconds. Get velocity, Reynolds number, friction factor, pressure drop, and a recommended commercial pipe size — instantly.

Inputs Saved

Added on top of the fittings list below.
ΣK = 0.00
K-values are typical handbook estimates (Crane TP-410 / Idelchik) — verify against your spec for design work.

Results

Recommended Pipe Size
Based on typical max velocity for the selected fluid.
Velocity
m/s
Reynolds Number
Friction Factor (Darcy)
Swamee–Jain
Pressure Drop
kPa
Cross-section area, A
Density, ρ
Viscosity, μ
Roughness, ε
Relative roughness, ε/D
Friction loss (f·L/D)
Fitting loss (ΣK)

Method. Friction factor uses the explicit Swamee–Jain correlation for turbulent flow (4000 ≤ Re ≤ 1×10⁸; valid for ε/D between 1×10⁻⁶ and 0.01). Laminar flow (Re < 2300) uses f = 64/Re. Pressure drop follows the Darcy–Weisbach equation: ΔP = (f·L/D + ΣK) · ρV² / 2. Recommended sizes pick the smallest schedule-40 commercial pipe meeting typical max-velocity guidance for the chosen fluid. Always validate against the applicable code (ASME B31, ASHRAE, ISO 4126, etc.) before specifying.