Motors & Loads calculator
Motor Power Calculator
Enter voltage, current, phase, power factor, efficiency, torque, and speed to compare electrical input power with shaft output using common U.S. motor formulas. For DC motors it uses P = V x I. For single-phase AC it uses P = V x I x PF. For balanced three-phase AC it uses P = sqrt(3) x V_L x I_L x PF. Mechanical shaft power uses HP = torque x RPM / 5252 and kW = HP x 0.746. Treat the results as an engineering check, not as a substitute for motor nameplate data, NEC Article 430 design work, or NEMA and IEEE test data.
Updated July 16, 2026
Enter voltage, current, phase, power factor, efficiency, torque, and speed to compare motor input kW, shaft HP, kVA, kVAR, and losses before carrying the result into nameplate and NEC 430 workflows.
Electrical mode compares input power, kVA, and kVAR | Mechanical mode compares torque, speed, and shaft HP
Choose electrical, mechanical, or efficiency mode below to compare kW, HP, torque, and losses, then carry the result into the motor nameplate worksheet before current and protection review
Calculator Inputs
Calculation Results
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Field kit
Tools for motor power checks
Use the power estimate to plan measured voltage and current checks before documenting a motor condition.
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Calculation history
Example Calculations
More examples. Open to review 1 additional calculation example.
How to Use
How to use the motor power calculator
This tool supports electrical power, mechanical power, efficiency review, and combined motor checks for U.S. field and design work.
1. Choose the calculation mode
- Electrical Power: Calculates input kVA, kW, reactive power, and electrical horsepower from voltage, current, motor type, and power factor.
- Mechanical Power: Calculates shaft horsepower, shaft kW, and watts from torque and speed.
- Efficiency Analysis: Estimates useful output and losses from electrical input and efficiency.
- Power Conversion: Converts the calculated electrical input into kW, HP, watts, BTU/hr, and ft-lb/s.
- Complete Analysis: Runs the electrical, mechanical, and efficiency checks together for one operating point.
2. Enter the right electrical inputs
For DC motors, the calculator uses P = V x I. For single-phase AC motors, it uses P = V x I x PF. For balanced three-phase AC motors, it uses P = √3 x V_L x I_L x PF. Use measured or nameplate-aligned values, and make sure voltage and current describe the same operating point.
3. Enter torque and speed for shaft power
If you need shaft output, enter torque in lb-ft and speed in rpm. The calculator applies HP = Torque x RPM / 5252 and converts that value to kW and watts.
4. Review efficiency and application limits
Use the calculated values to compare operating points, estimate losses, and cross-check field measurements. For formula running-current comparison, continue with the Motor Current Calculator. For NEC table full-load current lookup, use the Full Load Current Calculator. For downstream overload and branch-circuit protection review, use the Motor Protection Calculator.
5. Turn the power result into the next field check
After the kW, HP, or shaft-output result is known, document the nameplate voltage, phase, service factor, efficiency, and power factor assumptions before sizing the downstream circuit. Use the Motor Nameplate Data Worksheet to record that basis, the HP to Amps Chart for a quick current comparison, and the Wire Size Calculator only after the motor current and duty assumptions are clear.
Common Applications
More applications. Open to review 2 additional use cases.
Frequently Asked Questions
What is the motor power formula?
For DC motors, input power is P = V x I. For single-phase AC motors, real input power is P = V x I x PF. For balanced three-phase AC motors, real input power is P = √3 x V_L x I_L x PF. Shaft output uses HP = Torque x RPM / 5252 when torque and speed are known.
How do I calculate three-phase motor input power?
For a balanced three-phase motor, real input power in kilowatts is P = √3 x V_L x I_L x PF / 1000. Apparent power is S = √3 x V_L x I_L / 1000. The calculator uses that relationship when you select an AC motor type with three phases.
How do I calculate single-phase motor power?
For single-phase AC motors, the calculator uses P = V x I x PF / 1000 for real power and S = V x I / 1000 for apparent power. Enter the measured voltage, current, and power factor above so the result stays tied to the actual operating point instead of a generic worked example.
Does calculated motor current replace NEC Table 430.250 values?
No. Calculated input current helps with operating-point checks, but NEC Table 430.250 full-load current values are still the standard starting point for many U.S. conductor and overcurrent sizing rules. Use this tool as a design aid, then complete the NEC review separately.
Related Calculators
Motor Current Calculator
Estimate formula running current from HP or kW, voltage, efficiency, and power factor, then compare against NEC table FLC when needed.
Full Load Current Calculator
Owns NEC Table 430.248/430.250 FLC lookup by HP, voltage, and phase, including 10 HP and 200 HP at 460V field checks.
Motor Starter Calculator
Screen NEMA starter size, controller current class, overload-relay basis, and basic control-package notes.
Motor Efficiency Calculator
Operating-point screen for measured efficiency, input power, losses, and annual energy comparison at one shaft load.
Motor Torque
Open the motor torque for related motors & loads review.
Three Phase Motor Calculator
Balanced three-phase operating-point screen for line current, input kW, kVA, kVAR, and estimated shaft output.