sumivo

Sumivo · Electrical

Motor Current from Electrical Input Power

Estimate current for a single-phase motor from electrical input power, RMS voltage, and power factor.

01 / INPUTS

W
V
0–1

Single-phase calculation; power factor must be greater than 0 and at most 1.

02 / RESULT

SINGLE-PHASE CURRENT

5.11508951 A

Current
5.11508951 A
Power factor
0.85

Calculation trace

  1. 1,000 W ÷ (230 V × 0.85) = 5.11509 A
    5.11508951 A
    Single-phase current

Maintained by Jack Shi

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How it works

For single-phase AC, current is I = P ÷ (V × power factor), where P is electrical real input power in watts and V is RMS voltage. Shaft-output power is different: if the shaft rating is known, first divide it by efficiency (as a fraction) to obtain electrical input power. For example, 800 W shaft output at 80% efficiency requires 1000 W electrical input. The calculator does not assume an efficiency.

Assumptions & limits

  • Single-phase; you supply the power factor.
  • Enter electrical input power at the operating load, not shaft-rated watts. Power factor and efficiency are distinct ratios.

Verified runs

Synthetic examples executed at build revision 24533ff on . Cards round decimal results to 6 significant figures; matching uses full precision and the tolerance below. Matches cover the displayed fields, not every possible input or clinical or engineering validation.

  • Inputs: Electrical input power: 1000 W electrical input; Voltage: 230 V; Power factor: 0.85 ratio

    Result: Current: 5.11509 A (expected Current: 5.1151 A) ✓

  • Inputs: Electrical input power: 1000 W electrical input; Voltage: 230 V; Power factor: 0 ratio

    Result: Rejected: Power factor must be a finite number greater than 0 and at most 1. (expected Rejected) ✓

  • Inputs: Electrical input power: 746 W electrical input; Voltage: 120 V; Power factor: 1 ratio

    Result: Current: 6.21667 A (expected Current: 6.2167 A) ✓

How these runs were checked

Method: motor-current-1ph@1.0.0. Expectations come from the listed test fixtures or hand arithmetic; they are not copied from these executions. Omitted optional inputs use the method defaults. Run dates record execution, not expert review or fresh measurements.

Download all verified runs (JSON) — full inputs, returned values, expectations, timestamps and buildRevision.

  • normal: . Absolute tolerance: 0.0005. Text and booleans match exactly. Full-precision result: Current: 5.115089514066496 A. Expected: Current: 5.1151 A. Expectation: packages/calculator-core/tests/motor-current.test.ts
  • boundary: . Absolute tolerance: 1e-10. Text and booleans match exactly. Full-precision result: Rejected: Power factor must be a finite number greater than 0 and at most 1.. Expected: Rejected. Expectation: packages/calculator-core/tests/motor-current.test.ts
  • sensitivity: . Absolute tolerance: 0.0005. Text and booleans match exactly. Full-precision result: Current: 6.216666666666667 A. Expected: Current: 6.2167 A. Expectation: packages/calculator-core/tests/motor-current.test.ts

Reproduce from the source checkout with pnpm --filter @sumivo/web gen:verified-runs. A rebuild changes execution times; the revision identifies its Git starting point, including any uncommitted changes made for that build.

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FAQ

Does this work for three-phase motors?
No. Three-phase current uses I = P ÷ (√3 × V × power factor); this tool is single-phase.
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Related calculators

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SOURCES

  • OpenStax, Rice University
    University Physics Volume 2 ↗

    Electrical input power and power factor: single-phase current I = P ÷ (V × power factor)

    Accessed 2026-09-02