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Gurukrupa Enterprises
Electrical Calculators

1 Phase Current Calculator

Calculate single-phase current from load power, voltage and power factor.

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About this calculator

This calculator finds the current drawn by a single-phase AC load from its power, supply voltage and power factor. It is the standard formula used for sizing single-phase circuit breakers, cables and switches for pumps, small compressors and general loads.

Formula

I = (P × 1000) ÷ (V × PF)
  • PLoad power — kW
  • VSupply voltage — volts
  • PFPower factor — 0–1
  • ILine current — amperes

Worked Example

Given: A 3 kW single-phase load runs on 230V with a power factor of 0.9.

Result: I = (3 × 1000) ÷ (230 × 0.9) = 14.49 A.

How to Use

  1. Enter the load's real power in kW (from the nameplate or measured value).
  2. Enter the supply voltage (commonly 230V for single-phase in India).
  3. Enter the power factor — use the nameplate value, or 0.85–0.95 as a typical estimate if unknown.
  4. Click Calculate to get the current in amperes.

Important Assumptions

  • Assumes a resistive/inductive AC load at steady state, not motor starting (inrush) current.
  • Power factor must be entered as a decimal between 0.1 and 1.

Common Mistakes

  • Using apparent power (kVA) in place of real power (kW) in the formula.
  • Forgetting the power factor and assuming PF = 1, which understates the actual current.

Frequently Asked Questions

What power factor should I use if it isn't on the nameplate?

For general resistive/inductive industrial loads, 0.85 to 0.9 is a reasonable estimate; motors often run 0.8–0.9 at full load.

Does this include motor starting current?

No — starting (inrush) current for motors can be 5–7 times the running current shown here and needs separate calculation.

Should I size the breaker exactly to this current?

No. Cable and breaker sizing should include safety margins and follow the applicable electrical code — this calculator only gives the running current.

These calculators are provided for informational and estimation purposes. Results depend on the assumptions and input values used. Always verify critical engineering calculations against applicable standards, manufacturer specifications, site measurements, and qualified professional advice.