Amps to Volts Calculator
Find voltage from current (amps) using either real power (watts) for DC/AC circuits or resistance (ohms) with Ohm’s law. Power mode supports single- and three-phase AC with power factor. All calculations run in your browser.
Uses P = V × I (and AC forms with PF). Same physics as our Watts ↔ Amps tools, solving for V.
RMS line current for AC modes.
Real power in watts (not VA).
Table of Contents
Why you need another quantity besides amps
Amps alone do not determine volts. Current is only one variable in the relationships that link voltage, power, and impedance.
If you know real power in watts and current, you can solve for voltage using the same forms as P = V × I (DC) and the AC variants with power factor and √3 for balanced three-phase.
If you know resistance and current, Ohm’s law gives V = I × R — useful for resistive branches and many DC problems.
Choose the mode that matches what you know. Our Amps to Watts and Watts to Amps calculators use the same AC/DC assumptions for consistency.
Formulas
From power and current
DC
V (V) = P (W) ÷ I (A)
Rearrangement of P = V × I. Power factor does not apply.
AC single-phase
VRMS (V) = P (W) ÷ (I (A) × PF)
Real power P, RMS current I, and power factor PF (0–1).
AC three-phase (balanced)
VL-L (V) = P (W) ÷ (√3 × I (A) × PF)
Result is line-to-line RMS voltage. √3 ≈ 1.732. Same balanced-motor assumptions as our other electrical calculators.
Ohm’s law
V (V) = I (A) × R (Ω)
For a single resistive element or equivalent resistance. Reactive AC loads need phasor analysis — this mode is resistive/DC.
Quick Reference Table
| Method | Circuit | Current | P or R | PF | Voltage | Example |
|---|---|---|---|---|---|---|
| Power | DC | 10 A | 120 W | — | 12 V | Small DC load |
| Power | AC 1φ | 12 A | 2,736 W | 0.95 | 240 V | ≈ 240 V RMS |
| Power | AC 3φ | 10 A | 6,462 W | 0.9 | 415 V | VL-L (AU industrial) |
| Ohm’s law | — | 2 A | 50 Ω | — | 100 V | Resistor |
FAQ
No — you need either power (watts) and current or resistance (ohms) and current (or another complete relationship).
Use power mode when you have nameplate or metered watts and measured or rated current. Use Ohm’s law when you have a known resistance and current through it.
Yes — same formulas rearranged to solve for V instead of I.
For balanced three-phase real power: P = √3 × VL-L × I × PF. Solving for VL-L gives P ÷ (√3 × I × PF).