Ohm's Law: Power
P = VI = I²R = V²/R
How to Use This Calculator
Provide any two of V, I, and R. The calculator uses the appropriate formula to compute power in watts.
Formula
P = VI = I²R = V²/R
Frequently Asked Questions
What about AC circuits?
For AC, use real power P = VI cosφ. These formulas assume DC or resistive loads.