volts to amps

I = V ÷ R. Voltage drives current through a resistance, so a resistance value is required: 12 V across 4 Ω is 3 A. Where power is known instead, the identical result comes from I = P ÷ V.

Volts alone do not make amps — you need the resistance or the power that the voltage is pushing against. The US residential standard of 120 V only becomes a current when a load is connected: a 1,800 W space heater on a 120 V circuit draws 15 A, and that is the number a breaker is rated for. This calculator does the Ohm's law work: current equals voltage divided by resistance, or power divided by voltage.

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

Authority: NIST SP 811 (SI usage guide) and the 1959 International Yard and Pound Agreement. The coefficient above is a defined value — it does not come from measurement and carries no uncertainty.

volts to amps

Ohm's law is the single most used formula in electrical work: I = V/R. For power calculations, the watt's law companion P = V·I gives I = P/V. The US grid delivers 120 V to branch circuits; the 240 V used for ranges and dryers doubles the power for the same current. Every breaker, fuse, and wire-gauge decision in the US runs through this conversion — a breaker protects a circuit by current, and you choose it by converting the connected load's watts to amps at the circuit's voltage.

amps = volts ÷ ohms  (or  amps = watts ÷ volts)
I = V/R  ·  I = P/V
The calculation is Ohm's law and watt's law — exact, with the voltage from your circuit.

Worked Examples

Example 1: Find the current through 8 Ω at 120 V

120 ÷ 8 = 15 A

Example 2: Find the current through 16 Ω at 240 V

240 ÷ 16 = 15 A

Example 3: Find the current through 4 Ω at 12 V

12 ÷ 4 = 3 A

Common volts to amps Values

voltsohmsampsContext
120 V8 Ω15 AUS branch circuit at 8 Ω load — full breaker rating.
120 V6 Ω20 AKitchen appliance circuit.
240 V16 Ω15 AElectric dryer circuit.
240 V10 Ω24 ARange circuit, 30 A breaker.
12 V4 Ω3 AAutomotive accessory circuit.

Engineering Context

The volts-to-amps conversion is the root of the electric hub — from it come watts to amps (P/V), volts to ohms (V/I), and the whole Ohm's law family. The power side links to the energy hub's watts to kW and kW to watts, since breaker sizing feeds appliance energy estimates. The AWG side of the same circuit design lives in the AWG to mm² converter.

Volts do not produce amps without something to push against, and this page makes the point sharply: the same 120 volts drives 15 amperes through 8 ohms and 0.12 amperes through one thousand ohms. That dependence on resistance is what makes electrical safety counter-intuitive. A voltage high enough to are across dry skin is much higher than the 120 volts of a wall socket, because dry skin may present a hundred thousand ohms and limit the current to about a milliampere, while wet skin or a path across the chest can fall to a few hundred ohms and pass a lethal current at the same voltage. The hazard is the current, and the current depends on the path, not on the number on the supply.

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

Related Unit Converters

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

Frequently Asked Questions

How do I convert volts to amps?

You need a second quantity: current (A) = voltage (V) ÷ resistance (Ω), or current = power (W) ÷ voltage (V). A 120 V circuit with an 8 Ω load draws 15 A; the same circuit loaded to 1,800 W also draws 15 A.

How many amps is 120 volts?

It depends on the load. 120 V with no load draws 0 A. With a 1,800 W heater it draws 15 A; with a 60 W bulb, 0.5 A. Volts are the pressure; amps are the flow — the load determines the flow.

Is household voltage 120 or 240 volts in the US?

Both. US homes receive 240 V split into two 120 V legs: standard outlets use one leg at 120 V, while ranges, dryers, and HVAC use both legs for 240 V. That is why this converter matters at both voltages.