Voltage Calculator
Calculate electrical voltage from current and resistance, or from power and current. Also shows power dissipation for any circuit.
A
Ω
Voltage
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Power —
Current —
How to Use This Calculator
- Select whether to solve from current + resistance or power + current.
- Enter the two known values.
- Results show voltage and power.
Formula
V = I × R (current × resistance)
V = P ÷ I (power ÷ current)
Power: P = V × I = V² ÷ R = I² × R
Example
Example: I = 2 A, R = 10 Ω → V = 20 V, P = 40 W.
Frequently Asked Questions
- Use V = I × R (Ohm's Law). Multiply current in amps by resistance in ohms to get voltage in volts.
- Use V = P ÷ I, where P is power in watts and I is current in amps.
- Voltage drop is the reduction in voltage across a component due to its resistance. Use V = I × R where R is the wire or component resistance.
- DC voltage is constant (like a battery). AC voltage alternates direction and is described by RMS (root mean square) values. This calculator uses DC or RMS values.
- In the US, standard household voltage is 120 V AC at 60 Hz. In Europe it is 230 V AC at 50 Hz.