Voltage Drop Calculator

Calculated using standard mathematical and industry formulas.

Free online Voltage Drop Calculator calculator and unit conversion tool for everyday, engineering, and home projects.

How to use this calculator?

1. Select wire gauge.
2. Enter length and load.
3. Check NEC 3% drop rule.

Formula & calculation method

NEC Voltage Drop

VD = (2 × K × I × L) / CM

Single phase drop.

Step-by-step calculation example

15A 120V over 100ft 12 AWG copper = 2.97V (2.47%).

Key insights to remember

• NEC recommends ≤ 3% drop.

How to interpret your results?

% Voltage Drop

Percentage loss.

Frequently asked questions

How do I use the Voltage Drop Calculator calculator?

Enter your numerical input and select desired units to get instant accurate results.

How accurate are the conversions?

Conversions use official ISO conversion factors for maximum precision.

Does it convert metric and imperial units?

Yes, seamless conversions between metric (meters, kg) and imperial (feet, lbs) are supported.

Is my data stored?

No, all calculations execute 100% locally in your browser with zero data logging.

Can I use this for DIY or engineering projects?

Yes, it provides reliable estimates for construction, crafting, science, and everyday math.

What if I enter invalid inputs?

The calculator will display a friendly error prompt if non-numeric values are entered.

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