volts
Leave blank to solve for it.
amps
Leave blank to solve for it.
ohms
Leave blank to solve for it.
watts
Leave blank to solve for it.
Output
Output will appear here
Click in the output to select all text
Ohm's Law Calculator
Related tools
Featured
Comprehensive Multi-Unit Converter
Convert across 10+ categories: Length, Weight, Temperature, Area, Volume, Speed, Energy, Pressure, Power, and Data Storage.
Unit converterConversion
Power Unit Converter
Convert between Watts (W), Kilowatts (kW), Megawatts (MW), Horsepower (hp), and BTU/h.
Power converterWatts
Energy & Work Unit Converter
Convert between Joules, Kilojoules, Calories, Kilocalories (kcal), kWh, and BTU.
Energy converterJoules
This Ohm's Law calculator solves for voltage, current, resistance, and power in a simple DC circuit — enter any two of the four values and it computes the rest using V=IR and P=VI. It's useful for students learning basic circuit theory, hobbyists sizing resistors for an LED or sensor, and anyone double-checking a quick electrical calculation. Enter exactly two known values, leave the other two blank, and the calculator instantly fills in the complete picture along with all four quantities for reference. Everything runs locally in your browser. Scroll down to enter your known values.
Features
- Solves for any two of voltage, current, resistance, or power
- Uses standard Ohm's Law (V=IR) and power equation (P=VI)
- Shows all four values together for reference
- Instant recalculation as you change inputs
- Clear error messages for invalid combinations
Why use this ohm's law calculator?
- No need to remember which formula variant to rearrange
- Reduces manual arithmetic errors
- Fully private — nothing is uploaded
- Free with unlimited use
Frequently asked questions
What is Ohm's Law?
Ohm's Law states that voltage equals current multiplied by resistance (V = I × R) in a simple DC circuit.
How is power related to voltage and current?
Electrical power equals voltage multiplied by current (P = V × I); combined with Ohm's Law, power can also be derived from any two of V, I, or R.
How many values do I need to enter?
Enter exactly two of the four values (voltage, current, resistance, power); the calculator solves for the remaining two.
Does this work for AC circuits?
This calculator uses simple resistive DC circuit formulas; AC circuits with reactance/impedance require additional calculations not covered here.
Can resistance or current be zero?
Resistance and current of exactly zero are excluded from certain combinations because they'd require dividing by zero — the calculator will explain when that happens.