Volts to Watts Calculator
Convert voltage to power for DC, AC single-phase, and AC three-phase circuits
What is a Volts to Watts Calculator?
The Volts to Watts Calculator is a free online electrical tool that converts voltage (V) to power (W) when you know either the current (A) or the resistance (Ω). Volts measure electrical pressure — the force that pushes electrons through a circuit. Watts measure electrical power — the rate at which energy is consumed or produced. You cannot convert volts to watts directly because they measure different properties. You always need a second value: either current (amps) or resistance (ohms). This calculator handles DC circuits, AC single-phase circuits, and AC three-phase circuits with power factor support.
Why Use This Calculator?
Converting volts to watts manually requires different formulas depending on the circuit type. DC circuits use P = V × I, AC single-phase circuits add a power factor (P = V × I × PF), and three-phase circuits use √3 in the formula. This calculator eliminates the complexity — enter your values and get instant, accurate results with the formula shown step by step. Electricians use this to calculate power loads, engineers use it for circuit design, and homeowners use it to check appliance power consumption.
Volts to Watts Formula
The complete set of formulas for converting voltage to power
DC Volts to Watts Calculation
Direct current circuits use the simplest volts to watts formula
DC volts to watts conversion uses the formula P(W) = V(V) × I(A). Direct Current (DC) flows in one constant direction — batteries, solar panels, USB chargers, and automotive systems produce DC power. The DC volts to watts formula does not require a power factor because DC has no reactive power component. Simply multiply voltage by current to get power in watts.
A 12 V DC battery delivers 5 A of current. Power = 12 V × 5 A = 60 W. A 24 V solar panel producing 8.33 A delivers 24 × 8.33 = 200 W of power.
Single Phase
AC conversions require a power factor (PF) because not all power is used effectively
AC single-phase volts to watts conversion uses P(W) = V(V) × I(A) × PF. Single-phase AC power is standard in residential wiring. The power factor (PF) ranges from 0 to 1 and represents how effectively the circuit uses power. Resistive loads like heaters have PF ≈ 1.0, while motors and compressors have PF = 0.7 to 0.9.
A 120 V outlet powering an appliance drawing 10 A with PF = 0.85: P = 120 × 10 × 0.85 = 1020 W.
Three Phase & Resistance Method
Line-to-Line Voltage
Line-to-line voltage is measured between any 2 phase conductors. Use this for motor loads and three-phase equipment. √3 ≈ 1.732.
A 480 V three-phase motor draws 10 A with PF = 0.85: P = 1.732 × 480 × 10 × 0.85 = 7066.56 W.
Line-to-Neutral Voltage
Line-to-neutral voltage is measured between a phase conductor and the neutral point. Use this for single-phase loads on a three-phase panel.
A 277 V line-to-neutral system with 10 A and PF = 0.9: P = 3 × 277 × 10 × 0.9 = 7479 W.
Volts to Watts using Resistance
Convert volts to watts using resistance with the formula P(W) = V²(V) ÷ R(Ω). This formula combines Watt's Law and Ohm's Law. Use this conversion when a multimeter reads resistance instead of current. This formula applies to both DC and AC circuits.
A 120 V circuit with a 144 Ω heater element: P = 120² ÷ 144 = 14400 ÷ 144 = 100 W.
Example Calculations
Step-by-step volts to watts conversion examples
DC Battery System
Given: Voltage (V) = 24 V, Current (I) = 10 A
AC Single-Phase Appliance
Given: Voltage (V) = 120 V, Current (I) = 12 A, PF = 0.9
Using Resistance (No Current Known)
Given: Voltage (V) = 240 V, Resistance (R) = 48 Ω
Volts to Watts Conversion Chart
Quick reference table for common voltage and current values (DC)
| Voltage (V) | Current (A) | Power (W) |
|---|---|---|
| 5 V | 1 A | 5 W |
| 5 V | 5 A | 25 W |
| 5 V | 10 A | 50 W |
| 12 V | 1 A | 12 W |
| 12 V | 5 A | 60 W |
| 12 V | 10 A | 120 W |
| 24 V | 1 A | 24 W |
| 24 V | 5 A | 120 W |
| 24 V | 10 A | 240 W |
| 48 V | 1 A | 48 W |
| 48 V | 5 A | 240 W |
| 48 V | 10 A | 480 W |
| 120 V | 1 A | 120 W |
| 120 V | 5 A | 600 W |
| 120 V | 10 A | 1,200 W |
| 240 V | 1 A | 240 W |
| 240 V | 5 A | 1,200 W |
| 240 V | 10 A | 2,400 W |
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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 watts is 120 volts?
120 volts equals different wattages depending on the current (amps). At 1 A, 120 V = 120 W. At 5 A, 120 V = 600 W. At 10 A, 120 V = 1200 W. At 15 A, 120 V = 1800 W. The formula is P = 120 V × I(A). You must know the current to calculate watts from volts.
How to convert volts to watts without amps?
Convert volts to watts without amps by using resistance (ohms). The formula is P = V² ÷ R. For example, 120 V with 144 Ω resistance: P = 120² ÷ 144 = 14400 ÷ 144 = 100 W. You can measure resistance with a multimeter. Without either current or resistance, you cannot convert volts to watts.
What is the formula for volts to watts?
The volts to watts formula depends on the circuit type. DC: P(W) = V(V) × I(A). AC Single-Phase: P = V × I × PF. AC Three-Phase (Line-to-Line): P = √3 × V × I × PF. Using Resistance: P = V² ÷ R. All formulas require at least one additional value beyond voltage.
How many watts is 12 volts?
12 volts produces different wattages depending on the current. At 1 A: 12 W. At 5 A: 60 W. At 10 A: 120 W. At 20 A: 240 W. Common 12 V applications include car batteries (typically 40-60 A = 480-720 W), LED strips (1-5 A = 12-60 W), and USB devices (0.5-3 A = 6-36 W).
Is voltage the same as wattage?
No, voltage and wattage are different electrical properties. Voltage (volts) measures electrical pressure — the force that pushes electrons through a circuit. Wattage (watts) measures electrical power — the rate of energy consumption. Think of voltage as water pressure and wattage as the total water flow rate. You need both voltage and current to determine wattage: P(W) = V(V) × I(A).
How do you calculate watts from volts and amps?
Multiply volts by amps to get watts: P(W) = V(V) × I(A). For example, 120 V × 10 A = 1200 W. For AC circuits, also multiply by the power factor: P = V × I × PF. For three-phase AC, use P = √3 × V × I × PF for line-to-line voltage.
How many watts is 240 volts?
240 volts equals different wattages depending on the current. At 10 A: 2400 W. At 15 A: 3600 W. At 20 A: 4800 W. At 30 A: 7200 W. 240 V circuits are used for large appliances like dryers (5400 W), ovens (3000-5000 W), and air conditioners (2000-5000 W).
Can you convert volts to watts directly?
No, you cannot convert volts to watts directly because they measure different things. Volts measure electrical pressure; watts measure electrical power. You need at least one additional value: current in amps (P = V × I) or resistance in ohms (P = V² ÷ R). Without a second value, volts alone cannot determine watts.