Watts to Amps Calculator

Convert watts to amps (or reverse amps to watts) with voltage, phase, and power factor—instant bidirectional W ↔ A for appliances, heaters, and AC feeder pre-checks.

Power formula (1φ): W = V × I × PF · I = W ÷ (V × PF). Resistive/DC: PF ≈ 1 so W ≈ V × I. Example: 1800 W ÷ 120 V = 15 A. Three-phase √3 teaching → 3-Phase Power.

Calculator

Quick: watts + voltage → amps. Advanced: amps → watts, solve voltage from W & A (voltage↔watts), three-phase √3, and adjustable PF.

Solve for Covers voltage to watts / watts to voltage searches—enter any two of W, A, V.

Real power (W) Example: 1800 W heater. For kW, enter watts (10 kW = 10000).

Voltage (V)

Three-phase: use line-to-line voltage. Hidden when solving for voltage.

Power factor (PF) Resistive ≈ 1.0; motors/UPS often 0.80–0.95.

Phase

Single Phase Three Phase

About this calculator

This watts to amps calculator solves any two of W, A, V (with phase and PF)—including voltage to watts and watts to voltage. It is not a kVA→amps converter—use kVA to Amps when the nameplate is in kVA. For √3 teaching and three-phase worked examples, see the 3-Phase Power Calculator. Browse the power calculator hub.

Calculation Results

≈ 15 A (1.800 kW real power)

1800 W · 120 V · PF 1 · Single Phase

Formula: I = W ÷ (V × PF)

Balanced-load estimate from real power. Harmonics, motor starting, and continuous-load 125% breaker margins are not applied here.

Continue Your Calculation

Have line current from watts? Continue to breaker frame screening (link updates from your result).

Breaker size →

Watts to amps quick reference (PF 1.0)

Single-phase resistive: I = W ÷ V. Click a row to load the calculator.

Power	Voltage	Current
	120 V 1φ	8.33 A
	120 V 1φ	15 A
	240 V 1φ	12.5 A
	240 V 1φ	20.8 A
	480 V 3φ PF 0.85	≈ 14.15 A
	120 V 1φ	2400 W

Watts to amps formula (W = V × I × PF)

The core watts formula relates real power, volts, and amps. On AC circuits multiply by power factor; on DC or unity-PF resistive loads, PF ≈ 1 and W ≈ V × I (volts × amps).

Single-phase: I = W ÷ (V × PF) · W = V × I × PF · V = W ÷ (I × PF)

Three-phase (line current): I = W ÷ (V × √3 × PF) · W = V × I × √3 × PF · V = W ÷ (I × √3 × PF)

W — real power (watts); not the same as VA (apparent power)
V — RMS voltage (line-to-line for 3φ)
I — line current (amps)
PF — power factor (0–1); use 1.0 for heaters / many DC nameplates

W vs VA: Watts = VA × PF. If the nameplate is in kVA (not kW), convert current with kVA to Amps instead of this watts formula.

DC note: For DC, set phase to single-phase and PF = 1.0 (W = V × I). This page still solves any two of W, V, A.

Example: 1800 W ÷ (120 V × 1.0) = 15 A.

Deep three-phase √3 teaching and kW/kVA from V·A·PF → 3-Phase Power Calculator. Need kW ↔ kVA first? kW to kVA.

When to use which power tool

Goal	Tool
Convert watts ↔ amps (real power)	This page
Convert kVA ↔ amps (apparent power)	kVA to Amps
Convert kW ↔ kVA with PF	kW to kVA
Three-phase kW/kVA from V·A·PF	3-Phase Power
Pick breaker frame from amps	Breaker Size

Frequently Asked Questions

How do I convert watts to amps?

Single-phase: I = W ÷ (V × PF). Three-phase: I = W ÷ (V × √3 × PF). Example: 1800 W at 120 V PF 1.0 = 15 A.

How do I convert voltage to watts?

You need current as well: W = V × I × PF (1φ) or W = V × I × √3 × PF (3φ). Choose Watts (from amps + voltage) in Solve for. Example: 120 V × 15 A × PF 1.0 = 1800 W.

How do I convert watts to voltage?

Choose Voltage (from watts + amps): V = W ÷ (I × PF) (1φ). Example: 1800 W ÷ 15 A = 120 V at PF 1.0.

How do I convert amps to watts?

Single-phase: W = V × I × PF. Three-phase: W = V × I × √3 × PF. Example: 15 A at 120 V PF 1.0 = 1800 W.

Do I need power factor for watts to amps?

Yes for AC real power. Resistive loads can use PF ≈ 1.0. Motors and UPS loads often use 0.8–0.95. If you already know kVA, use kVA to Amps instead.

What is 1000 watts in amps at 120V?

At 120 V single-phase PF 1.0: ≈ 8.33 A. At PF 0.9: ≈ 9.26 A. Use the 1000 W preset above.

Is watts to amps the same as kVA to amps?

No. Watts need PF; kVA does not. This page owns W↔A; kVA to Amps owns apparent-power current.

What is the watts formula (W = V × I)?

For DC or resistive AC at PF 1.0: W = V × I. For AC real power generally: W = V × I × PF (1φ) or W = V × I × √3 × PF (3φ). Example: 120 V × 15 A × PF 1.0 = 1800 W. Deep √3 teaching → 3-Phase Power.

Is watts equal to volts times amps?

Only when PF = 1.0 (or on DC). Otherwise watts = volts × amps × PF. VA (apparent) is V × I without PF; W (real) needs the PF term—see the formula section above.