3-Phase Power Calculator
Calculate 3-phase motor power output.
About the 3-Phase Power Calculator
This 3-phase power calculator computes total power in watts, kilowatts, or amps for any balanced three-phase system. Use it to size service entrance equipment, verify motor loads against nameplate ratings, calculate utility demand for industrial billing, and right-size transformers for new installations.
Defaults match common Canadian voltages: 208V (light commercial), 480V (industrial), and 600V (heavy industrial — unique to Canada). The formula assumes a balanced three-phase system, which is the normal case for industrial loads.
How 3-phase power is calculated
The standard balanced three-phase power formula:
P (watts) = √3 × V × I × PF
kW = (√3 × V × I × PF) ÷ 1000
The √3 (1.732) factor accounts for the 120-degree phase angle between the three phases. Line-to-line voltage equals √3 times line-to-neutral voltage in a balanced system. For apparent power (kVA), drop the power factor: kVA = (√3 × V × I) ÷ 1000.
Worked example
A 480V three-phase motor draws 30 amps at 0.85 power factor. Real power consumed: P = 1.732 × 480 × 30 × 0.85 = 21,196 watts (21.2 kW). Apparent power: kVA = 1.732 × 480 × 30 = 24,940 VA (24.9 kVA). The 14.5% gap between kVA and kW reflects the 0.85 PF.
Common Canadian three-phase voltages
- 208V three-phase: light commercial, small industrial. Line-to-neutral 120V.
- 240V three-phase: legacy delta systems, some agricultural. Line-to-neutral varies (high-leg).
- 480V three-phase: standard industrial. Line-to-neutral 277V (used for HVAC and industrial lighting).
- 600V three-phase: Canadian heavy industrial standard. Line-to-neutral 347V (Canadian fluorescent lighting).
- 4160V/13.8kV: medium-voltage industrial distribution and large motor applications.
The 600V system is unique to Canada (and a few US states near the border). It’s preferred for heavy industrial because higher voltage means lower current, which means smaller conductors and less voltage drop over long runs.
When to use this calculator
- Sizing breakers and conductors for a new 3-phase machine installation
- Verifying measured motor amperage against nameplate rating
- Calculating peak utility demand for industrial billing analysis
- Specifying VFDs by required output kW
- Right-sizing transformers for new equipment additions
- Troubleshooting power quality issues by comparing measured vs expected current
- Validating power monitoring software readings
Frequently Asked Questions
How do you calculate 3-phase power?
P (watts) = √3 × Voltage × Current × Power Factor. For 480V at 30A and 0.85 PF: P = 1.732 × 480 × 30 × 0.85 = 21,196 W = 21.2 kW.
What is √3 (1.732) in 3-phase calculations?
It accounts for the 120-degree phase angle between the three phases of an AC system. Mathematically, the line-to-line voltage in a balanced three-phase system equals √3 times the line-to-neutral voltage. Without this factor you would underestimate total power by about 42%.
Should I use line-to-line or line-to-neutral voltage?
For the standard 3-phase power formula above, use line-to-line voltage (208V, 480V, 600V in Canada). If you only know line-to-neutral voltage, multiply by √3 first or use a different formula: P = 3 × VLN × I × PF.
What is the difference between kVA and kW in 3-phase systems?
kVA = √3 × V × I (no PF) is apparent power — what your equipment must be sized to handle. kW = √3 × V × I × PF is real power — what does useful work and what you pay for. The ratio is power factor.
How do I calculate amps from 3-phase kW?
Rearrange the formula: I = (kW × 1000) ÷ (V × √3 × PF). For 25 kW at 480V and 0.85 PF: I = 25,000 ÷ (480 × 1.732 × 0.85) = 35.4 amps.
Why is 600V used in Canadian industrial facilities?
600V allows smaller conductors for the same power (since amps are lower), which reduces wire cost and voltage drop on long runs. It’s the Canadian Electrical Code’s standard heavy-industrial voltage. The US equivalent (480V) is more common globally.
Does this formula work for unbalanced loads?
Strictly only for balanced loads where all three phases carry the same current. For significantly unbalanced systems, calculate each phase separately and sum. In most industrial settings (motors, balanced lighting), unbalance is under 5% and the formula is accurate enough for sizing.
3-Phase Power Quick Reference
Three-phase power at 30 A and 0.85 power factor across common North American voltages. Scale linearly for other currents (e.g. 60 A = double the kW).
| Voltage | Current | Real Power (kW) | Apparent (kVA) |
|---|---|---|---|
| 208 V | 30 A | 9.0 kW | 10.8 kVA |
| 240 V | 30 A | 10.4 kW | 12.5 kVA |
| 480 V | 30 A | 20.8 kW | 24.9 kVA |
| 600 V | 30 A | 26.0 kW | 31.2 kVA |
Common 3-Phase Power Questions
How do you calculate 3-phase power?
Multiply the square root of 3 (1.732) by voltage, current and power factor: Watts = √3 × V × A × PF. For 480 V at 30 A and 0.85 PF that is 1.732 × 480 × 30 × 0.85 = 21,196 W (21.2 kW).
How many amps is a 3-phase motor?
Rearrange the formula: Amps = (kW × 1000) ÷ (√3 × V × PF). For a 25 kW load at 480 V and 0.85 PF that is about 35.4 A.
Related calculators and motor categories
Sizing equipment for your 3-phase load? Browse General Purpose motors, Explosion Proof motors, or HVAC motors from Baldor, WEG, Marathon, and U.S. Motors.
Related calculators: kVA to Amps Calculator · kW to kVA Calculator · Cable Sizing Calculator · Generator Sizing Calculator.
