Single Phase Motor Capacitor Calculator

Enter your motor’s details below to estimate the correct start and run capacitor size in microfarads (µF) for a single phase motor — used in washing machines, air coolers, fans and pumps.

Motor Power

Power Unit

Supply Voltage (V)

Frequency (Hz)

Power Factor (cos φ)

Efficiency (%)

Please enter a valid motor power greater than zero.

Estimated Result

Motor Power	–
Run Capacitor	–
Start Capacitor (approx.)	–
Recommended Capacitor Voltage Rating	–

These are engineering estimates based on standard single-phase induction motor formulas (C = P × 10⁶ ⁄ (2π × f × V² × (1 − PF))). Always cross-check with the motor’s nameplate or the manufacturer’s datasheet before installing a capacitor, since exact winding design can shift the ideal value. Never install a capacitor rated below the motor’s supply voltage.

How to Use This Single Phase Motor Capacitor Calculator

Every single phase induction motor — the type found in washing machines, air coolers, ceiling fans, and water pumps — needs a capacitor to create the phase shift required for starting torque. Using the wrong capacitor size can cause the motor to hum without starting, overheat, or fail early. This single phase motor capacitor calculator uses standard motor engineering formulas to give you a reliable starting point.

Simply enter the motor's power (in HP, kW, or Watts), supply voltage, frequency, power factor and efficiency, and the calculator will instantly estimate the run capacitor and start capacitor values in microfarads (µF), along with a safe voltage rating for the capacitor.

Formula Used

Run capacitor value is calculated using:

C (µF) = P × 10⁶ ÷ (2π × f × V² × (1 − PF))

Where P = motor input power in watts, f = frequency in Hz, V = supply voltage, and PF = power factor. The start capacitor is generally taken as roughly twice the run capacitor value, following standard single-phase motor design practice.

Frequently Asked Questions

Q: What happens if the capacitor is too big or too small?
A: An oversized capacitor can overheat the motor and reduce its lifespan, while an undersized capacitor won't provide enough starting torque, causing the motor to struggle or fail to start.

Q: Can I use this for a 3-phase motor?
A: No, this calculator is designed specifically for single phase motors. Three phase motors do not require starting capacitors.

Q: Is this an exact value?
A: This is an engineering estimate. Always confirm with the motor's nameplate or the manufacturer's datasheet where available, since exact winding design can shift the ideal value slightly.

Need to convert measurements while sizing your motor setup? Try our Online Length Unit Converter.