What is an acceptable voltage drop?

The NEC recommends no more than 3% voltage drop for branch circuits and 5% total (feeder plus branch). Exceeding these limits can cause equipment malfunction, motor overheating, and dimming lights.

How does wire gauge affect voltage drop?

Larger wire gauges (lower AWG numbers) have lower resistance per foot, which reduces voltage drop. For example, 10 AWG has about 1.21 ohms per 1000 ft compared to 1.93 for 12 AWG.

Why is the formula different for three-phase circuits?

Three-phase circuits use a sqrt(3) multiplier instead of 2 because the return current is shared among three conductors rather than flowing through a single neutral wire.

Voltage Drop Calculator

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About Voltage Drop Calculator

Voltage drop occurs when current flows through wire resistance. This calculator uses Vdrop = 2 x I x R x L / 1000 for single-phase and Vdrop = sqrt(3) x I x R x L / 1000 for three-phase circuits, where R is the NEC Chapter 9 Table 8 resistance per 1000 ft. It checks the NEC recommendation that voltage drop should not exceed 3% for branch circuits or 5% total.

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FAQ

What electrical engineering calculations can this tool perform?

This tool handles LED resistor sizing (R = (Vs - Vf) / I), wire voltage drop (NEC Chapter 9 tables), conduit fill analysis (NEC fill limits), and power factor correction (power triangle with capacitor sizing).

Are the results accurate?

Yes. All calculations use deterministic algorithms and NEC/IEEE reference data. Every result is mathematically guaranteed to be correct.

Is this electrical engineering calculator free?

Yes! All electrical engineering calculations are completely free with detailed step-by-step explanations. No account required.

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