Pump: Size | Delivery Height || Drain

Pump Size Calculator

Calculate the volumetric flow rate, volume, time, diameter and speed of a pump. Here you can calculate, how much water (or any other liquid) a pump can handle theoretically. This quantity is given as volume V. The volumetric flow rate V/t is the amount per time, can therefore also be seen as a kind of velocity, but should not be confused with v. Diameter d refers to the opening diameter of the round outlet, where the water comes out. The velocity v is the flow velocity at this point. The higher the flow rate, the more powerful the pump. The maximum possible flow rate can be referred to as the pump size.

Volume V:		MillilitersCentilitersLitersCubic meters
Time t:	d, h, min, s
Volumetric flow rate V/t:		cm³lm³ / dhmins
Diameter d:		MillimetersCentimetersMeters
Velocity v:		m/skm/h

Round to   0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15   decimal places.

Please select the desired units. Then enter two values ​​for volume, time, and volumetric flow rate; the third of these values ​​will be calculated. Furthermore, one of the three values - volumetric flow rate, diameter, and velocity - can be calculated from the other two. So, this calculator essentially consists of two parts: one for the volumetric flow rate and one for the flow velocity.
Time t is specified in days (d), hours, minutes, and seconds.

The formula for this calculation is: V/t = (d/2)² * π * v

If the diameter is given in centimeters, the flow rate in meters per second, and the time in seconds in the above formula, then the unit for volume is square centimeters times meters. This equals one-tenth of a liter. cm² * m = 1/10 l

The relevant quantity for the water outlet is not the diameter, but the area. If the outlet is circular, which is the case in most cases, then this area is calculated as (d/2)² * π. If the outlet actually has a different shape, then the formula for its area can be substituted for this position in the above formula.

Last updated on 12/13/2025. Author: Jürgen Kummer

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