Process Engineering · Fluid Flow

Line Sizing Calculator

Gas and liquid line sizing against a min/max velocity window, real-gas (Z-factor) density, compressible-flow pressure drop for gas, and lifecycle-cost pipe diameter — in metric or field units.

Basis — real gas law · Colebrook–White · Darcy–Weisbach (liquid) / compressible ΔP (gas)
Erosional limit API RP 14E, C=100
1Fluid conditions
Real-gas density: ρ = P(abs)·MW / (Z·R·T). Use 1.0 to fall back to ideal gas.
2Flow
Solves the isothermal flow equation for downstream pressure using Colebrook–White f — general-purpose, any pipe size.
E derates Weymouth/Panhandle for pipe condition (0.85–1.0). k is used for the Mach/choke check only.
3Velocity & sizing criteria
min · max
Sizing keeps velocity inside this window. The max is also capped by the API RP 14E erosional limit automatically, whichever is lower.
4Pipe spec
Auto picks the smallest standard size that lands inside the velocity window and under the allowable pressure drop.
5Fittings & valves
Minor loss adds ΣK·(ρV²/2) to the friction pressure drop, using velocity and density at the selected pipe size. ΣK = 0
6Economics
$/m of installed pipe at bore D (inches). Placeholder — replace with a vendor quote or estimating curve.

Recommended line size

—

Bore — · actual velocity —

auto-recommended
—

Required bore range

ID min (at V max)
—
ID max (at V min)
—
V max used
—
Erosional limit
—
Any standard bore between ID min and ID max keeps velocity inside your window. D = √(4Q/πV), evaluated at V max (lower bound) and V min (upper bound).

Pipe size comparison — Sch

NPSIDVelocityVelocity statusRefΔP /100ΔP status

Pressure conversion

Gauge—
Absolute—
kPa (abs)—
psi (abs)—
atm (abs)—
kg/cm² (abs)—

Temperature conversion

Celsius—
Kelvin—
Fahrenheit—
Rankine—

Flow rate conversion

kg/h—
kg/s—
lb/h—
——

Density & volumetric flow

Density—
Density—
Volumetric flow—
Volumetric flow—
—

Reynolds number

—
—
Re = 124.01 · ρ(lb/ft³)·V(ft/s)·D(in) / μ(cP)

Friction factor

Relative roughness (ε/D)—
Darcy friction factor, f—
—

Pressure drop — selected size

Over entered length—
Per 100—
Allowable—
—

Economic pipe diameter

Capital (annualized) Operating (energy) Total annual cost
Velocity-based pick
—
Economic optimum
—
Total annual cost, at the two picks
—
NPSIDVelocityΔPCapital $/yrOperating $/yrTotal $/yr
Capitalannual = a·D(in)b·L · CRF(i,n)  ·  Operatingannual = (Q·ΔP/η)·hours·energy cost  ·  picks the lowest total annualized cost across the same schedule and pipe table used above.