Voltage Calculator
Calculate voltage from current and resistance using Ohm’s law, plus dissipated power.
Estimates based on Ohm’s law for ideal DC circuits. Verify against local electrical codes and consult a qualified electrician for real installations.
How it works
- 1Enter the current in amperes (A).
- 2Enter the resistance in ohms (Ω).
- 3The calculator applies V = I × R and shows the dissipated power P = V × I.
Use cases
- Finding the voltage across a resistor in a DC circuit.
- Checking expected voltage for a known load current and resistance.
- Confirming voltage and wattage requirements when sizing a supply.
Frequently asked questions
What is the formula for voltage?
Voltage V = I × R (Ohm’s law). For example, 2 A through a 10 Ω resistor produces 20 V.
Can I find voltage from power instead?
Yes — rearrange P = V × I to V = P ÷ I. At 40 W and 2 A the voltage is 20 V.
Does this work for AC circuits?
It applies to purely resistive loads where V = I × R. With capacitors or inductors you must use impedance (Z) instead of resistance.
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