How to Calculate Flow Rate from RPM

The RPM to Flow Rate Calculator determines the flow rate based on pump speed (RPM), pump displacement, and efficiency. The base formula (in GPM) is:

Where:

• \( FR \): Flow Rate (in selected unit: GPM or L/min).
• \( RPM \): Pump speed in revolutions per minute.
• \( D \): Pump displacement (converted to in³/rev; e.g., 1 cm³/rev ≈ 0.061 in³/rev, 1 L/rev ≈ 61.024 in³/rev).
• \( \eta \): Volumetric efficiency (input as %, divided by 100).
• 231: Conversion factor (1 gallon = 231 in³).

For L/min, multiply GPM by 3.7854. Enter values and select units to calculate.

Formula source: Mechanical Design Engineering: ENABLER Project – Wheel & Wheel Drives (NASA CR-192060, 1992)

https://ntrs.nasa.gov/api/citations/19930008862/downloads/19930008862.pdf

Using the RPM to Flow Rate Calculator

This calculator is useful for engineers working with pump systems, accounting for units and efficiency.

Input pump speed (RPM), displacement (with unit), efficiency (%), and select flow rate unit. The calculator converts displacement to in³/rev, applies efficiency, computes in GPM, and converts to L/min if selected.

Example: For 1800 RPM, displacement of 32.8 cm³/rev, 95% efficiency, output in L/min:

1. Pump Speed: \( 1800 \, \text{RPM} \)
2. Displacement: \( 32.8 \, \text{cm}^3/\text{rev} \approx 2 \, \text{in}^3/\text{rev} \)
3. Efficiency: \( 95\% = 0.95 \)
4. GPM: \( \frac{1800 \times 2 \times 0.95}{231} \approx 14.805 \, \text{GPM} \)
5. L/min: \( 14.805 \times 3.7854 \approx 56.026 \, \text{L/min} \)
6. Result: \( 56.026 \, \text{L/min} \)

Use this tool for accurate pump flow calculations.

Common FAQ

Below are frequently asked questions about RPM to Flow Rate calculations:

• Q: What is RPM?
  A: RPM stands for revolutions per minute, measuring the speed of a pump's rotation.
• Q: What is Flow Rate?
  A: Flow rate measures the volume of fluid moved, in GPM (gallons per minute) or L/min (liters per minute).
• Q: Why include efficiency?
  A: Efficiency accounts for losses in the pump; typically volumetric efficiency as a percentage.
• Q: How are units converted?
  A: Displacement is converted to in³/rev internally; flow rate is computed in GPM and converted to L/min if selected (1 GPM ≈ 3.7854 L/min).
• Q: Can negative values be used?
  A: No, RPM, displacement, and efficiency must be positive; invalid inputs leave the result blank.
• Q: How do I find the pump displacement?
  A: Pump displacement is typically provided in the pump's technical specifications, in various units.