Inputs
Example data table
| Scenario | Flow | Suction (abs) | Discharge | Stages | Model | Motor input (hp) | Suggested motor |
|---|---|---|---|---|---|---|---|
| Site tools baseline | 350 CFM (actual) | 101.325 kPa | 110 psi (gauge) | 1 | Adiabatic | ≈ 88 hp | 100 hp |
| Higher pressure setup | 300 CFM (actual) | 101.325 kPa | 175 psi (gauge) | 2 | Adiabatic | ≈ 100 hp | 125 hp |
| Energy-focused estimate | 200 CFM (actual) | 101.325 kPa | 90 psi (gauge) | 1 | Isothermal | ≈ 32 hp | 40 hp |
Examples are illustrative. Your equipment and conditions can shift results significantly.
Formula used
This calculator estimates compressor power using ideal-gas relations, then applies efficiency factors for realistic sizing.
- Isothermal: kW = P₁ · Q · ln(P₂/P₁)
- Adiabatic: kW = (k/(k−1)) · P₁ · Q · [(P₂/P₁)^((k−1)/k) − 1]
- Multi-stage: r = (P₂/P₁)^(1/N), total is the sum of stage power.
- Losses: Air-end = Ideal/η_comp, Shaft = Air-end/η_mech, Motor = Shaft/η_motor
Internally, kPa and m³/s are used so kPa·m³/s = kW. Horsepower uses 1 hp = 0.7457 kW.
How to use this calculator
- Enter inlet flow and choose the correct units.
- Set suction absolute pressure (often 101.325 kPa).
- Enter discharge pressure and select gauge or absolute.
- Choose a compression model and number of stages.
- Adjust efficiencies to match your compressor and motor.
- Press Calculate to see results above the form.
- Download CSV or PDF for submittals and logs.
Use the recommended motor size for planning, then verify using manufacturer performance curves and site conditions.