Three-Phase Amperage Calculator

Enter power and voltage to compute line current (A). Includes power factor, efficiency, and Show Work.

How to Use

  1. Select your input power type (kW or HP).
  2. Enter voltage (typically line-to-line for 3-phase systems).
  3. Set power factor and efficiency if needed.
  4. See results + step-by-step work below. Use Share Link only when ready.
System Readout
Outputs update instantly (no URL changes while typing).
I (Line)
—
kVA
—
kW
—
PF
—
Current band: —
Formula used (balanced 3φ): I = P / (√3 × VL-L × PF × η)
Inputs & Settings
Supports kW or HP inputs. Power factor and efficiency are optional.
Common: motors in HP, loads in kW. (HP assumes mechanical output unless you adjust η.)
Tip: Most 3φ nameplates use line-to-line (208, 240, 480, 600).
PF is typical for AC motors/inductive loads. Use 1.0 for purely resistive.
If power input is electrical kW, set η=1.0. If power is mechanical HP, η matters.
Show Work (step-by-step)
—
Work is shown using base units (W, V, A). Assumes balanced three-phase unless noted.

Reference

  • Balanced 3φ: P = √3 × VL-L × I × PF × η
  • Line current: I = P / (√3 × VL-L × PF × η)
  • Apparent power: S (VA) = √3 × VL-L × I
  • kVA: kVA = VA / 1000
Note: For non-balanced loads, harmonics, VFDs, or code sizing, use nameplate and applicable electrical code.

FAQ

Do I use line-to-line or line-to-neutral voltage?

For standard three-phase current calculations, use line-to-line (e.g., 208V, 480V, 600V). If you only know line-to-neutral, this tool can convert it to line-to-line internally.

What PF should I use for a motor?

Motors commonly run around 0.80–0.95 depending on load and size. If unknown, start with 0.85 and compare to nameplate.

When does efficiency matter?

If your input power is electrical kW (metered input), set η=1.0. If your input is mechanical output (HP), use motor efficiency to estimate electrical input.

Is this for delta or wye?

The √3 relationship holds for balanced systems regardless of delta/wye when you use the correct line-to-line voltage for the system.

Tool Info

Last updated:

Updates may include more presets, better rounding, and edge-case handling (PF/η bounds, voltage mode helpers).