Amps to Volts Calculator
Enter current in amps and resistance in ohms to calculate voltage using Ohm's Law (V = I × R). Works for DC and resistive AC circuits.
How do you convert amps to volts?
Use Ohm's Law: volts = amps × ohms. A 5 A current through a 24 Ω resistance gives 5 × 24 = 120 V. You need both current and resistance — amps alone cannot give volts. Rearranged, current I = V ÷ R and resistance R = V ÷ I.
Amps to Volts Formula (Ohm's Law)
Ohm's Law states that voltage across a conductor is equal to the current through it multiplied by its resistance. V = voltage (volts), I = current (amperes), R = resistance (ohms). Rearrangements:
Also show how all four Ohm's Law quantities relate to power:
Understanding Ohm's Law
A simple way to understand Ohm's Law is to think of water flowing through a pipe. Voltage (V) represents the water pressure pushing the water, current (I) represents the flow rate of the water, and resistance (R) represents the pipe diameter limiting the flow. Increasing the pressure (voltage) or widening the pipe (lowering resistance) increases the flow (current).
Amps to Volts Reference Table (V = I × R)
| Current | 1 Ω | 4 Ω | 8 Ω | 12 Ω | 24 Ω | 100 Ω | 1000 Ω |
|---|---|---|---|---|---|---|---|
| 0.1 A | 0.1 V | 0.4 V | 0.8 V | 1.2 V | 2.4 V | 10 V | 100 V |
| 0.5 A | 0.5 V | 2 V | 4 V | 6 V | 12 V | 50 V | 500 V |
| 1 A | 1 V | 4 V | 8 V | 12 V | 24 V | 100 V | 1000 V |
| 2 A | 2 V | 8 V | 16 V | 24 V | 48 V | 200 V | 2000 V |
| 5 A | 5 V | 20 V | 40 V | 60 V | 120 V | 500 V | 5000 V |
| 10 A | 10 V | 40 V | 80 V | 120 V | 240 V | 1000 V | 10000 V |
| 15 A | 15 V | 60 V | 120 V | 180 V | 360 V | 1500 V | 15000 V |
| 20 A | 20 V | 80 V | 160 V | 240 V | 480 V | 2000 V | 20000 V |
Ohm's Law in the Real World: Voltage Drop
Electricians use the Amps-to-Volts relationship (V = I × R) constantly to calculate voltage drop over long wire runs. When current flows through a wire, the wire's natural resistance consumes some voltage, leaving less for the device at the end.
- 100 ft of 12 AWG extension cord (0.32 Ω total loop resistance) carrying 15 A:
Voltage lost = 15 A × 0.32 Ω = 4.8 Volts. If your wall outlet provides 120 V, your tool only receives 115.2 V. - 200 ft of 14 AWG wire (1.0 Ω total loop) carrying 12 A:
Voltage lost = 12 A × 1.0 Ω = 12 Volts. A 10% drop on a 120 V circuit is unacceptable per the NEC, as motors will run hot and burn out. - Poor electrical connection (0.5 Ω contact resistance) carrying 20 A:
Voltage lost = 20 A × 0.5 Ω = 10 Volts. This 10 V drop at the bad connection generates heat (P = I × V = 20 × 10 = 200 W), which is enough to melt a receptacle and start a fire.
Frequently Asked Questions
How do I convert amps to volts?
Use Ohm's Law: V = I × R, where V is voltage in volts, I is current in amps, and R is resistance in ohms. Example: 5 A through 24 Ω = 5 × 24 = 120 V.
What formula converts amps to volts?
V = I × R (Ohm's Law). Rearranging: I = V ÷ R; R = V ÷ I. You need both current and resistance to find voltage — amps alone are not sufficient.
How many volts is 10 amps at 12 ohms?
V = 10 × 12 = 120 V.
Can I convert amps to volts without resistance?
No. Voltage depends on both current and resistance (V = I × R). Without knowing the resistance of the circuit, the conversion is not mathematically possible. Use a multimeter to measure resistance if it is unknown.
What is the relationship between amps, volts, and watts?
P (watts) = V (volts) × I (amps). Combined with Ohm's Law: P = I² × R and P = V² ÷ R. Use these when you know any two quantities to find the third. See our Watts to Amps and Amps to Watts calculators.
How does resistance affect the voltage my appliance gets?
According to Ohm's law (V = I × R), any resistance in the wire or connections will 'consume' some voltage as current flows. The more amps you draw, or the higher the resistance (longer/thinner wires), the more voltage is lost as heat before reaching your appliance.