About

Sizing circuit breakers, fuses, and wire gauges requires knowing the current draw in Amperes (I). However, transformers and generators are typically rated in Volt-Amperes (S). This tool converts Apparent Power to Current. The conversion depends heavily on the circuit phase configuration. A common error in electrical planning is treating a 3-Phase load like a Single-Phase load, which leads to undersized wiring and potential fire hazards.

For industrial applications involving motors or large distribution panels, select the appropriate Voltage Reference (Line-to-Line vs. Line-to-Neutral) to ensure accuracy.

Formulas

The relationship between Apparent Power (S) and Current (I) is defined by Ohm"s Law for AC circuits.

Single Phase:

I = SV

Three Phase (Line-to-Line Voltage):

I = SV_LL × √3

where √3 ≈ 1.732

Reference Data

System Voltage	Phase	Common Application	Formula Ref
120 V	1 Φ	US Residential Outlets	I = S / V
240 V	1 Φ	US Residential Dryers/Ovens	I = S / V
208 V	3 Φ	US Commercial HVAC/Motors	I = S / (V×√3)
230 V	1 Φ	EU/UK Residential	I = S / V
400 V	3 Φ	EU/UK Industrial	I = S / (V×√3)
480 V	3 Φ	US Industrial Heavy Equipment	I = S / (V×√3)

Frequently Asked Questions

The tool allows you to select the unit. 1 kVA equals 1,000 VA. Ensure you select the correct unit dropdown to avoid calculating currents that are off by a factor of 1,000.

In 3-phase systems, voltage measured between two live wires is Line-to-Line (e.g., 480V or 400V). Voltage measured between one live wire and neutral is Line-to-Neutral (e.g., 277V or 230V). Most equipment nameplates specify Line-to-Line voltage.

This conversion is strictly between Apparent Power (VA) and Amps. Power Factor is only needed when converting to Real Power (Watts). Wire sizing is based on total current flow (Amps), which comes directly from VA.

For DC circuits, use the Single Phase calculation. VA is effectively equal to Watts in DC, so Current = Power / Voltage.