# Pipe diameter calculator

## round, closed, full pipe diameter calculation

This calculator is for quick pipe diameter computation in closed, round and fully filled pipes. Calculator is suitable for liquids and perfect gases.

Compute pipe internal diameter by using simple relation between flow rate, velocity and cross section area (Q=v·A). Enter fluid flow rate and velocity in corresponding fields in calculator and perform calculation. If flow rate or velocity is unknown, than please use other computation method, like one in pressure drop calculator .

With this calculator, you can also calculate flow velocity for given fluid flow rate and internal pipe diameter. As velocity is different on different places of pipe cross section area, flow mean velocity is computed based on the continuity equation.

Flow rate used in calculator can be in terms of mass or volume flow rate.

Conversion between mass and volume flow rate is possible for given fluid density. Also, volume flow rate conversion for different flow conditions (pressures and temperatures) is possible.

If flowing fluid is perfect gas, you can calculate volume flow rate of that gas at different pressures and temperatures. For example, if you know volume flow rate of some perfect gas at some predefined pressure and temperature (like at normal conditions p=101325 Pa and T=273.15 K), you can calculate actual volume flow rate for pressure and temperature that is actually in the pipe (for example, actual pressure and temperature in the pipe is p=30 psi and t=70 F). Volume flow rate of perfect gas will be different at these two conditions. Read more about normal conditions for pressure and temperature.

With this calculator you can convert volume flow rate from normal or some other predefined conditions to actual conditions and vice versa. Computation of volume flow rates for this two conditions is based on the mass conservation law, meaning that mass flow is constant, despite that conditions in terms of pressure and temperature are changing. This is true only if the flow is occuring in the closed pipe, without added or subtracted flow, if the flow is not changing in time and few other conditions. Read more about mass conservation law.