Calculate pump flow rate from RPM or find the RPM needed for a target flow, with advanced options for displacement and hydraulic power.

Choose the value you want to find. Enter the other two.
Revolutions per minute.
Volume moved per revolution.
Known flow rate.
▸ Advanced options
Use 100 for theoretical flow. Real pumps are often 85 to 97.
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RPM to Flow Rate Formula

The following two example problems outline the steps and information needed to calculate the RPM to Flow Rate.

FR = RPM * D / 231
  • Where FR is the RPM to Flow Rate (GPM)
  • RPM is the pump RPM 
  • D is the pump displacement (in^3/revolution) 

To calculate a flow rate from RPM, multiply the RPM by the displacement, then divide by 231.

RPM to Flow Rate Conversion Table (Displacement = 1.00 in³/rev, Efficiency = 1.00)
RPM Flow Rate (GPM) Flow Rate (L/min)
1000.4331.639
2501.0824.097
3001.2994.916
5002.1658.194
6002.5979.832
7503.24712.290
9003.89614.748
1,0004.32916.387
1,2005.19519.665
1,5006.49424.581
1,7507.57628.677
1,8007.79229.497
2,0008.65832.774
2,2009.52436.052
2,40010.39039.329
2,50010.82340.968
3,00012.98749.161
3,20013.85352.439
3,45014.93556.535
3,60015.58458.994
* Rounded to 3 decimals. Assumes Displacement = 1.00 in³/rev and Efficiency = 1.00. Formula: Q(GPM) = RPM × Displacement × Efficiency ÷ 231. Conversion: 1 GPM = 3.78541 L/min.

How to Calculate RPM to Flow Rate?

The following example problems outline how to calculate RPM to Flow Rate.

Example Problem #1:

  1. First, determine the pump RPM.
    • The pump RPM is given as: 400.
  2. Next, determine the pump displacement (in^3/revolution).
    • The pump displacement (in^3/revolution) is provided as: 2.5.
  3. Finally, calculate the RPM to Flow Rate using the equation above: 

FR = RPM * D / 231

The values provided above are inserted into the equation below and computed.

FR = 400 * 2.5 / 231 = 4.239 (GPM)

Example Problem #2: 

For this problem, the variables required are provided below:

pump RPM = 600

pump displacement (in^3/revolution) = 3

Test your knowledge using the equation and check your answer with the calculator..

FR = RPM * D / 231 = ?