Choose what you know
All six pairs of V, I, R, and P are supported.
Six known pairs · exact decimal prefixes
Solve the ideal relationship behind volts, amps, ohms, and watts.
OhmCalc accepts any two positive quantities, normalizes their units exactly, calculates the other two, and keeps every value in the browser.
No account, circuit upload, component recommendation, backend, or generated result URL.
Three visible decisions
Choose a pair, normalize units, inspect formulas
State each unit
Milli, micro, kilo, and mega are exact powers of ten.
Read the proof and boundary
The result shows formulas and approximation status, not a safety approval.
Focused electrical arithmetic
Useful equations without pretending to design a circuit
- Voltage from current and resistance or power.
- Current in amps or milliamps.
- Resistance in ohms or kilo-ohms.
- Ideal resistive power in watts.
Two known values
Keep volts, amps, ohms, and watts in one visible relationship
Choose the known pair, normalize SI prefixes exactly, and inspect the formulas used for every result.