What the tool does, how to run it, and what to expect from the result.
Single-phase drop = 2 × one-way length × current × resistance per foot. 12 AWG copper is 1.93 Ω per 1,000 ft (NEC Chapter 9, Table 8), so 100 ft at 16 A drops 2 × 100 × 16 × 1.93 ÷ 1000 = 6.18 V, 5.15% of 120 V. Three-phase uses √3 instead of 2. The NEC recommends no more than 3% on a branch circuit.
A quick way to understand who this helps, what it solves, and where it connects next.
Students, lab workers, electricians and engineers who want the formula and the answer.
Using the voltage drop calculator without installing anything or signing up.
Short answers for the questions people usually have before trying a utility like this.
NEC informational notes suggest 3% on a branch circuit and 5% total including the feeder. It is a recommendation, not a code requirement.
Use a larger wire (lower AWG number), shorten the run, or raise the voltage.
Nearby tools from the catalog that fit the same job or workflow.
Solve V, I, R, or P
Enter any 2 of voltage, current, resistance, or power to get the other 2.
Survey sample size for a margin of error
Survey sample size for a margin of error. Free, instant, in your browser.
Vout from R1, R2
Enter the input voltage and 2 resistor values to get the output voltage.
Calculate your BMI
Calculate your Body Mass Index from height and weight, with a category. Free, in your browser, no sign-up.
Calculate percentages
Work out what one number is as a percentage of another, and percentage amounts. Free, in your browser, no sign-up.
Adjusted and ideal body weight for dosing
Adjusted and ideal body weight for dosing. Free, instant, in your browser.
Cleanor puts these tools in one app: compress and convert images, video, and audio, work with PDFs, and scan text right on your device. Plus free up storage and clear inbox clutter with Email Cleaner. Start with a free trial.
Enter your numbers and the result updates live in your browser. Nothing is uploaded and no server is used.
Uses NEC Chapter 9 Table 8 DC resistance at 75°C; AC drop can be slightly higher. Check the NEC and your inspector.