Volts to Amps Calculator
Convert voltage to current using Ohm's Law or Watt's Law
What is a Volts to Amps Calculator?
The Volts to Amps Calculator is a free online tool that converts voltage (V) to current (A) using either Ohm's Law (when resistance is known) or Watt's Law (when power is known). You cannot convert volts to amps directly because they measure different electrical properties — volts measure electrical pressure, while amps measure the flow of electrons. You always need a second value: resistance (Ω) or power (W). This calculator gives you the option to use either method, with support for AC power factor adjustments.
When to Use Ohm's Law vs Watt's Law?
Use Ohm's Law (I = V ÷ R) when you know the resistance of the circuit or component. This is common when working with resistors, heating elements, or when you've measured resistance with a multimeter. Use Watt's Law (I = P ÷ V) when you know the power rating of a device. This is common when checking if an appliance will fit on a circuit — the power (watts) is usually printed on the appliance label, and the voltage is your supply voltage.
Understanding Ohm's Law & Watt's Law
Volts to Amps using Resistance (Ohm's Law)
I = V ÷ R — the most fundamental electrical formula
Ohm's Law states that current equals voltage divided by resistance: I(A) = V(V) ÷ R(Ω). This law was described by Georg Simon Ohm in 1827 and is the foundation of electrical circuit analysis. Higher voltage pushes more current through a given resistance. Higher resistance limits the current for a given voltage.
A 12 V battery connected to a 6 Ω resistor: I = 12 ÷ 6 = 2 A. A 120 V outlet with a 10 Ω heating element: I = 120 ÷ 10 = 12 A.
Volts to Amps using Power (Watt's Law)
I = P ÷ V — use when power rating is known
Watt's Law rearranged gives current: I(A) = P(W) ÷ V(V). For AC circuits with a power factor: I = P ÷ (V × PF). This method is used when appliance labels show watts and you need to know the current draw for circuit breaker sizing.
A 1200 W hair dryer at 120 V: I = 1200 ÷ 120 = 10 A. A 2400 W oven at 240 V: I = 2400 ÷ 240 = 10 A.
Example Calculations
Step-by-step volts to amps conversion examples
Using Ohm's Law (Resistance Known)
Given: Voltage (V) = 120 V, Resistance (R) = 10 Ω
Using Watt's Law (Power Known)
Given: Voltage (V) = 240 V, Power (P) = 3600 W
AC with Power Factor
Given: Voltage (V) = 120 V, Power (P) = 1500 W, PF = 0.85
Volts to Amps Conversion Chart
Quick reference for common voltage and resistance combinations
| Voltage (V) | Resistance (Ω) | Current (A) |
|---|---|---|
| 5 V | 1 Ω | 5.00 A |
| 5 V | 10 Ω | 0.50 A |
| 5 V | 100 Ω | 0.05 A |
| 12 V | 1 Ω | 12.00 A |
| 12 V | 10 Ω | 1.20 A |
| 12 V | 100 Ω | 0.12 A |
| 24 V | 1 Ω | 24.00 A |
| 24 V | 10 Ω | 2.40 A |
| 24 V | 100 Ω | 0.24 A |
| 48 V | 1 Ω | 48.00 A |
| 48 V | 10 Ω | 4.80 A |
| 48 V | 100 Ω | 0.48 A |
| 120 V | 1 Ω | 120.00 A |
| 120 V | 10 Ω | 12.00 A |
| 120 V | 100 Ω | 1.20 A |
| 240 V | 1 Ω | 240.00 A |
| 240 V | 10 Ω | 24.00 A |
| 240 V | 100 Ω | 2.40 A |
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Volts to Watts Calculator
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Watts to Amps Calculator
Convert power (W) to current (A) for DC and AC circuits with power factor support.
Amps to Watts Calculator
Convert current (A) to power (W) for DC, AC single-phase, and AC three-phase circuits.
Volts to Amps Calculator
Convert voltage (V) to current (A) using Ohm's Law or Watt's Law.
Amps to Volts Calculator
Convert current (A) to voltage (V) using Ohm's Law or Watt's Law.
Frequently Asked Questions
How many amps is 120 volts?
120 volts alone doesn't tell you the amps — you need resistance or power. With a 1200 W device: I = 1200 ÷ 120 = 10 A. With a 12 Ω resistance: I = 120 ÷ 12 = 10 A. With a 1800 W device: I = 1800 ÷ 120 = 15 A. The amps depend on the load connected to the 120 V source.
How to convert volts to amps?
Two methods: (1) Ohm's Law — divide volts by resistance: I = V ÷ R. (2) Watt's Law — divide power by volts: I = P ÷ V. You need either resistance or power as a second value. Volts alone cannot be converted to amps.
What is the volts to amps formula?
There are two volts to amps formulas. Ohm's Law: I(A) = V(V) ÷ R(Ω) when resistance is known. Watt's Law: I(A) = P(W) ÷ V(V) when power is known. For AC circuits, add power factor: I = P ÷ (V × PF).
How many amps is 240 volts?
240 volts produces different amperages depending on the load. A 2400 W oven: I = 2400 ÷ 240 = 10 A. A 4800 W dryer: I = 4800 ÷ 240 = 20 A. A 48 Ω heating element: I = 240 ÷ 48 = 5 A. You always need resistance or power to determine amps.
Can you convert volts to amps without resistance?
Yes, if you know the power (watts). Use Watt's Law: I = P ÷ V. For example, a 600 W device at 120 V: I = 600 ÷ 120 = 5 A. Without either resistance or power, volts alone cannot be converted to amps.
How do volts and amps relate to each other?
Volts and amps are connected through Ohm's Law: V = I × R. Volts measure electrical pressure (force), amps measure electrical flow (rate). Higher voltage pushes more current through the same resistance. Doubling the voltage doubles the current if resistance stays constant. Think of volts as water pressure and amps as flow rate.
How many amps is 12 volts with a 6 ohm resistor?
12 volts with 6 ohms equals 2 amps: I = V ÷ R = 12 ÷ 6 = 2 A. This is a common calculation for automotive circuits and LED installations where 12 V DC is standard.
What is Ohm's Law in simple terms?
Ohm's Law says that current (amps) equals voltage (volts) divided by resistance (ohms): I = V ÷ R. In simple terms: more pressure (volts) pushes more flow (amps), but more resistance (ohms) reduces the flow. It's like a water pipe — higher pressure means faster flow, but a narrower pipe (more resistance) slows it down.