Pipe Diameter

A velocity range is a starting point, not a line specification.

Formula

Q = V × A

A = π × d² / 4

d = sqrt(4 × Q / (π × V))

Q is the volume flow you enter. V is a velocity you accept. d is the inside diameter. The minimum inside diameter uses the top of the velocity range, because a higher velocity gives a smaller bore. The inside diameter at the bottom of the range is shown as well. Density, if you enter it, is used only to report mass flow. It does not change the diameter.

1 L = 0.001 m³. A flow in m³/h is divided by 3600. 1 US gallon = 231 in³ = 231 × (0.0254 m)³, and US gpm is that volume divided by 60. 1 ft = 0.3048 m.

Water: Engineering Toolbox, water in steel pipe, 0.9–2.4 m/s (180–480 ft/min), low pressure up to 50 psi (3.5 bar), about 10–38°C. Not a code limit. https://www.engineeringtoolbox.com/fluid-velocities-pipes-d_1885.html

Light oil: Carl Branan, Rules of Thumb for Chemical Engineers, the published starting range for clean single-phase liquids, 1.5–4.0 m/s. This is that starting range. It is not an oil-grade table.

Viscous oil: no velocity range is stored. Enter the range you accept.

Steam: Engineering Toolbox, saturated steam at 0–30 psi, 20–30 m/s (4000–6000 ft/min) in steel pipe. Other steam conditions differ. Not a code limit. https://www.engineeringtoolbox.com/flow-velocity-steam-pipes-d_386.html

Gas: Carl Branan, Rules of Thumb for Chemical Engineers, the published starting range for clean single-phase gas, 15–40 m/s. Not a code limit.

Choosing a service fills the velocity boxes. You can type over them. Changing the velocity unit does not convert the numbers. Nominal size is not suggested unless a bore list is supplied, and that list is off by default. This page does not contain a B36.10 table. Numbers on the result line are rounded for display with six significant figures.