Volts to Amps Conversion Calculator

What volts to amps solves

Given a voltage and a resistance, how much current flows? That’s Ohm’s law read for current, and it’s the calculation behind checking whether a resistive load — a heating element, a resistor network, a length of nichrome wire — will draw more current than its circuit is rated for, before you plug it in.

The catch is right there in the word “resistive.” The formula is exact for anything whose resistance stays put as the voltage changes. It is not a way to predict the current a motor, an LED, a phone charger, or a TV will pull, because those loads don’t obey a fixed volts-to-amps ratio.

The volts to amps formula

is current in amps, is the voltage across the load in volts, and is its resistance in ohms. Nothing else enters into it — no power factor, no phase term — for a purely resistive load.

Worked example

The calculator’s defaults are 120 V across a 12 Ω load.

Ten amps. That’s a coherent snapshot of a standard circuit: a 12-ohm resistive element is about a 1,200 W heater, and 10 A is exactly what it draws from a 120 V outlet. On a 15 A branch circuit that leaves only 5 A of margin, and under the National Electrical Code’s continuous-load rule a circuit running three hours or more should be loaded to no more than 80% — 12 A on a 15 A circuit — so this load is close to that ceiling.

Volts to Amps Conversion Calculator worked example diagram — A visual read of the worked example above — the same numbers the calculator returns for its default inputs.

Voltage and resistance to current

Voltage	5 Ω	12 Ω	24 Ω	60 Ω	240 Ω
12 V	2.4 A	1.0 A	0.5 A	0.2 A	0.05 A
120 V	24 A	10 A	5 A	2 A	0.5 A
240 V	48 A	20 A	10 A	4 A	1 A

Halving the resistance doubles the current. That’s the relationship that makes a partial short circuit dangerous: as resistance collapses toward zero, current climbs toward whatever the supply and wiring will allow.

What the result assumes

The current returned assumes the resistance is fixed and the load is purely resistive. Real conductors and elements gain a few percent of resistance as they heat, so a value from a cold measurement predicts slightly more current than the circuit will draw once warm. For anything safety-critical, confirm the actual draw with a clamp meter rather than relying on a calculated figure.

Common mistakes

Applying it to non-resistive loads. A motor’s or power supply’s current comes from its nameplate, not from V ÷ R.
Using a cold resistance for a hot circuit. Heating elements can be several percent higher in resistance at operating temperature.
Confusing this with a power-based calculation. If you know watts rather than ohms, use amps = watts ÷ (volts × power factor) instead.

For the reverse, use the amps to volts calculator. To find current from power instead of resistance, see watts to amps, and for the power dissipated in the load, volts to watts.

About the formula: Use the stated electrical relationship and enter values in the displayed units.

Frequently Asked Questions

How does this volts to amps conversion calculation work?+

It applies Ohm's law: current equals voltage divided by resistance. Enter the voltage across the load and its resistance in ohms, and the calculator divides one by the other to give the current in amps.

How many amps does a 12-ohm load draw at 120 volts?+

120 ÷ 12 = 10 A. That's a self-consistent picture of a standard branch circuit — a 12-ohm resistive load is roughly a 1,200 W heater, and 10 A is what it pulls from a 120 V supply.

Does the resistance change with temperature?+

Usually yes. Copper and most heating elements gain resistance as they warm — about 0.4% per °C for copper — so a cold measurement reads low and the real running current is slightly less than a cold-resistance calculation predicts.

Is this accurate for motors, LEDs, or electronics?+

No. This simple form of Ohm's law only holds for a fixed-resistance load like a heater or a resistor. Motors, LEDs, and switch-mode supplies don't draw current in proportion to voltage, so their current has to come from a nameplate or a meter.

What if I know the power instead of the resistance?+

Use a power-based calculation instead: amps = watts ÷ (volts × power factor). This Ohm's-law version needs resistance specifically. The two approaches answer the same question from different starting information.

Does this give AC or DC current?+

Either, as long as the load is purely resistive. Enter RMS voltage and you get RMS current. For loads with meaningful inductance or capacitance, the opposition to current is impedance rather than resistance and this formula no longer applies.