Watts to Amps Calculator
Divides watts by volts (and PF / √3 when selected) to estimate current.
Limitation: Educational estimate only.
How to Use the Watts to Amps Calculator
Enter the fields below, then review the educational estimate.
Enter power in watts.
Nameplate vs measured
Use running watts when possible. Startup surge can be much higher than steady current.
What This Calculator Estimates
Estimates current from power and voltage using P = V·I·PF·k for single- or three-phase.
Worked Examples
1200 W heater on 120 V
Inputs
Result
I = 1200 / 120 = 10 A.
10 kW three-phase at 480 V, PF 0.9
Inputs
Result
I = P / (V·PF·√3).
Safety first
De-energize circuits before measuring. When in doubt, stop and consult a licensed electrician.
Frequently Asked Questions
Still have questions about this calculation?
Try the CalculatorFormulas & Assumptions
Transparent educational arithmetic. Not NEC design software or a wiring permit.
Formula
Single-phase / DC
I = P / (V · PF)
Three-phase
I = P / (V · PF · √3)
Scientific Background
Real power relates to apparent power by the power factor. This worksheet does not model harmonics, unbalanced phases, or motor inrush.
Sources & review
Watts to Amps Calculator documents the references behind its formulas and assumptions. Always treat results as educational estimates, not personalized professional advice.
Last reviewed
July 22, 2026
Reference
physics.nist.gov
https://physics.nist.gov/cuu/Constants/index.htmlReference
nist.gov
https://www.nist.gov/pml/owm/wire-gauge-and-current-carrying-capacityFree Calculator Hub methodology
Free Calculator Hub
/methodology
See our methodology and corrections policy.