Calculate compressed air power, flow rate, or pressure from any 2 values using P = Δp × Q and view results in kW, hp, CFM, bar, psi, or kPa.

Compressed Air (Pressure–Flow) Power Calculator

Enter any 2 values to calculate the missing variable (ideal relation: P = Δp × Q)

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Compressed Air Pressure-Flow Power Formula

The calculator uses the ideal pressure-flow power relationship. It converts your selected units to SI base units first, performs the calculation, then converts the result back to the unit you selected.

P = Δ p * Q
Q = P / Δ p
Δ p = P / Q
  • P = ideal pressure-flow power, in watts before unit conversion
  • Δp = pressure difference, in pascals before unit conversion
  • Q = volumetric flow rate, in cubic meters per second before unit conversion

If you leave Power blank, the calculator uses pressure and flow rate to calculate ideal pneumatic power. If you leave Flow Rate blank, it divides power by pressure difference. If you leave Pressure blank, it divides power by flow rate.

This is an ideal pressure-flow calculation. It does not include compressor efficiency, motor efficiency, heat effects, leakage, pressure drops through equipment, or the difference between actual CFM and standard CFM.

Pressure, Flow, and Power Unit Conversions

These are the conversion factors used before applying the formulas.

Quantity Unit SI conversion
Power W 1 W
Power kW 1 kW = 1000 W
Power HP 1 HP = 745.7 W
Flow rate m³/min 1 m³/min = 0.0166667 m³/s
Flow rate L/min 1 L/min = 0.0000166667 m³/s
Flow rate CFM 1 CFM = 0.000471947 m³/s
Pressure bar 1 bar = 100,000 Pa
Pressure psi 1 psi = 6,894.76 Pa
Pressure kPa 1 kPa = 1000 Pa

How to Read the Ideal Power Result

Result type What it means Important note
Ideal pneumatic power Power represented by pressure difference multiplied by volumetric flow. This is not the same as compressor electrical input power.
Pressure difference The pressure drop or pressure rise used in the calculation. Use differential pressure, not absolute pressure, unless that is specifically what your problem requires.
Flow rate The volumetric air flow used with the pressure difference. The CFM option is treated as ft³/min. It does not correct for standard air conditions.

Examples

Example 1: Calculate power from pressure and flow

You have a pressure difference of 8 bar and a flow rate of 1.5 m³/min.

  • Convert pressure: 8 bar = 800,000 Pa
  • Convert flow: 1.5 m³/min = 0.025 m³/s
  • Apply the formula: P = 800,000 × 0.025 = 20,000 W
  • Convert to kW: 20,000 W = 20 kW

The ideal pressure-flow power is 20 kW.

Example 2: Calculate flow rate from power and pressure

You have 5 HP of ideal pressure-flow power and a pressure difference of 90 psi.

  • Convert power: 5 HP = 5 × 745.7 = 3,728.5 W
  • Convert pressure: 90 psi = 90 × 6,894.76 = 620,528.4 Pa
  • Apply the formula: Q = 3,728.5 / 620,528.4 = 0.006008 m³/s
  • Convert to CFM: 0.006008 × 2118.88 = 12.73 CFM

The flow rate is about 12.73 CFM.

FAQ

Is this the same as compressor horsepower?

No. This calculator gives ideal pressure-flow power from P = Δp × Q. A real compressor needs more input power because of compression thermodynamics, heat, motor losses, mechanical losses, controls, and leakage. Use this result as ideal fluid power, not as the final motor size.

Should pressure be gauge pressure or absolute pressure?

Use the pressure difference, Δp. In many shop-air calculations, that means the gauge pressure difference across the device or process. For example, if air drops from 100 psi to 90 psi through a component, the pressure difference for that component is 10 psi.

Can I use SCFM in the CFM field?

The CFM field is converted as cubic feet per minute of volume flow. It does not apply standard-temperature or standard-pressure corrections. If your value is SCFM, make sure the pressure-flow relationship you are using is appropriate for standard flow, or convert to actual volumetric flow for the conditions at the point of interest.