What this converter does
This converter applies Ohm’s law to turn a current into the voltage it produces across a known resistance — or the reverse. Enter the resistance in ohms, type the amps, and read the volts. It updates as you type, useful for checking a voltage drop or a shunt reading.
Ohm’s law is the backbone of circuit analysis: voltage equals current times resistance. For AC power rather than pure resistance, see the Watts to Amps converter, which also takes voltage and power factor.
The units it covers
Ohm’s law links the three basic circuit quantities — the resistance you enter connects amps and volts.
View all units & their values
| Unit | Symbol | Value | Mainly used |
|---|---|---|---|
| Current | A | I | The flow of charge through the circuit |
| Voltage | V | V | The potential difference produced |
| Resistance | Ω | R | How much the component opposes current |
| Power | W | P | V × I, if you need the dissipation |
The formula
Voltage is current times resistance:
V = A × R (and A = V ÷ R)Where:
- A = the current through the component
- R = the resistance in ohms
- V = the resulting voltage in volts
Worked example
A 3 A current through a 4 Ω resistor. Find the voltage drop.
V = A × R3 × 4 = 12 VThe voltage across the resistor is 12 V — a 36 W dissipation at 3 A.
The units in this example
The rate of charge flow, in amperes. Multiplied by resistance it gives the voltage drop across a component.
- V = A × R
- 3 A × 4 Ω = 12 V
- A = V ÷ R
- P = V × I
The potential difference across a component, in volts. For a fixed resistance it rises directly with current.
- A = V ÷ R
- 12 V ÷ 4 Ω = 3 A
- 1 V = 1 joule per coulomb
- R = V ÷ A