amps to volts

V = I × R. Current becomes voltage through a resistance, so this is an Ohm’s law calculation rather than a unit conversion: 3 A through 4 Ω develops 12 V. If power is known instead, V = P ÷ I gives the same answer.

Amps become volts only when pushed through a resistance: V = I·R. A 15 A current through an 8 Ω load needs 120 V — the exact pair the US grid delivers. Power supply designers use this in reverse every day: to push a target current through a known load, they must supply the voltage this calculator returns.

By EnginStack Editorial Team | Reviewed against NIST, BIPM and primary-source documentation About →
amps
ohms
— volts
— —

Source: NIST SP 811 and the 1959 yard-and-pound agreement (0.9144 m, 0.45359237 kg). Every decimal place in the factor above is a defined constant, not a measurement.

amps to volts

Ohm's law works in any direction: V = I·R, or with power, V = P/I. The reverse direction is how a charger works — a phone charging at 2 A through an effective load needs the voltage its circuitry demands. Automotive 12 V systems, USB 5 V, and the 48 V of telecom racks are all answers to the same question: what voltage do these amps need?

volts = amps × ohms  (or  volts = watts ÷ amps)
V = I·R  ·  V = P/I
Exact Ohm's law calculation from the current and load you provide.

Worked Examples

Example 1: Find the voltage across a 15 A load of 8 Ω

15 × 8 = 120 V

Example 2: Find the drive voltage for a 10 A load of 1.2 Ω

10 × 1.2 = 12 V

Example 3: Find the supply for a 2 A load of 2.5 Ω

2 × 2.5 = 5 V

Common amps to volts Values

ampsohmsvoltsContext
15 A8 Ω120 VUS branch circuit pair.
20 A6 Ω120 VKitchen circuit pair.
30 A8 Ω240 VDryer circuit pair.
2 A2.5 Ω5 VUSB charger pair.
10 A1.2 Ω12 VAutomotive circuit pair.

Engineering Context

The amps-to-volts page is the inverse of volts to amps — V = I·R versus I = V/R. Together with volts to watts and watts to volts they cover the four-way Ohm/watt relationship. The electric hub collects all twelve converters, and the power side feeds the energy family.

Current does not become voltage on its own, which is why this page is a calculation rather than a unit conversion: it needs a resistance to complete it. That requirement is also the basis of a measurement technique. A current-sense resistor of known value turns an unknown current into a voltage that an analog-to-digital converter can read, and this is how clamp meters, motor drives and battery monitors measure current at all. A shunt of ten milliohms carrying one hundred amperes drops exactly one volt, a convenient scale, and the shunt is specified by its temperature coefficient because its own resistance drifts as it heats, which biases the reading it is supposed to produce.

More: V to A · W to V · V to Ω · Electric Guide · Electric Hub

Related Unit Converters

volts to amps watts to volts volts to ohms Electric Conversion Guide Electric Converters

Frequently Asked Questions

How do I convert amps to volts?

Multiply amps by resistance: V = I·R. Or divide power by current: V = P/I. A 15 A current through an 8 Ω load requires 120 V.

Why do phone chargers output 5 volts?

Because the USB standard chose 5 V as its baseline. The charger's circuitry converts mains voltage down to the level the device needs — and the device draws whatever current its load requires at that voltage.

Can I calculate volts without resistance?

Yes — if you know power: V = P/I. A 60 W device drawing 5 A needs 12 V. Either resistance or power completes the pair; volts alone are never computable from amps alone.