Volts to Amps Calculator
Find current from either power (A = P ÷ V) or resistance (A = V ÷ R).
How do you convert volts to amps?
You need one more quantity — power or resistance. If you know power, divide watts by volts: A = P ÷ V. A 60 W bulb on 120 V draws 60 ÷ 120 = 0.5 A. If you know resistance, use Ohm's law: A = V ÷ R, so 12 V across 4 Ω gives 12 ÷ 4 = 3 A. Voltage alone is never enough.
Volts to Amps Formulas
When you know the power a device consumes, current is power divided by voltage. Example: a 600 W tool on 120 V draws 600 ÷ 120 = 5 A.
On AC, divide by the power factor as well. A 1,000 W motor at 230 V with PF 0.9 draws 1,000 ÷ (230 × 0.9) = 4.83 A.
For a purely resistive load, current is voltage divided by resistance. Example: 24 V across 8 Ω gives 24 ÷ 8 = 3 A. This is the classic form of Ohm's Law.
Volts to Amps from Power (A = P ÷ V)
| Power | at 12 V | at 120 V | at 240 V |
|---|---|---|---|
| 60 W | 5.000 A | 0.500 A | 0.250 A |
| 100 W | 8.333 A | 0.833 A | 0.417 A |
| 500 W | 41.67 A | 4.167 A | 2.083 A |
| 1000 W | 83.33 A | 8.333 A | 4.167 A |
| 1500 W | 125.0 A | 12.50 A | 6.250 A |
Ohm's Law: How Resistance Controls Current
Using the Volts to Amps conversion (I = V ÷ R) allows you to predict how much current will flow based solely on the voltage and the physical resistance of a component. This is critical in electronics repair and heating element design:
- 12V Car Battery shorted by a 0.05 Ω dropped wrench:
Amps = 12 ÷ 0.05 = 240 A. This massive current will rapidly heat the wrench and potentially cause the battery to explode, demonstrating why short circuits are dangerous. - Testing a 240V Water Heater Element measuring 12.8 Ω:
Amps = 240 ÷ 12.8 = 18.75 A. A technician can use a multimeter to measure the resistance of the element while it's turned off, and use this formula to verify it will draw the correct ~19 amps when turned on. - Skin resistance touching a 120V live wire (dry skin, ~100,000 Ω):
Amps = 120 ÷ 100,000 = 0.0012 A (1.2 mA). You feel a mild tingle. If hands are wet (resistance drops to ~1,000 Ω), the current becomes 120 ÷ 1,000 = 0.12 A (120 mA), which is lethal.
Frequently Asked Questions
Can I convert volts to amps with only voltage?
No. Voltage alone does not set the current — it depends on the load. You also need either the power (watts) or the resistance (ohms). With power: A = P ÷ V. With resistance: A = V ÷ R.
What is the formula for volts to amps?
It depends on what else you know:
- From power (DC):
A = P ÷ V - From power (AC):
A = P ÷ (V × PF) - From resistance:
A = V ÷ R
How many amps is 120 volts?
On its own, 120 V is not a number of amps — the current depends on the load. A 60 W bulb on 120 V draws 0.5 A; a 1,500 W heater on 120 V draws 12.5 A. Enter the wattage above to get an exact answer.
How do I use Ohm's Law to find amps?
Divide voltage by resistance: A = V ÷ R. For example, 12 V across a 4 Ω load gives 12 ÷ 4 = 3 A. See Ohm's Law explained for the full V–I–R relationship.
Can high voltage exist without any amps flowing?
Yes. Voltage is just electrical pressure. If the circuit is open (infinite resistance), the voltage is present but the amps are zero (e.g. V ÷ ∞ = 0 A). Current (amps) only flows when there is a closed path (resistance) for the voltage to push against.