Voltage Drop Calculator
Last updated: June 2026 · Free · No sign-up required
Enter values above and click Calculate to see your result instantly.
Quick reference
Copper resistance by wire size (approx, ohms/1000 ft):
| AWG | Ohms/1000 ft |
|---|---|
| 14 | 2.525 |
| 12 | 1.588 |
| 10 | 0.999 |
| 8 | 0.628 |
| 6 | 0.395 |
apps Small jobs, done in one click
Everyday calculators are the workshop drawer of the site — quick utilities for the moments when you need a number now and a phone calculator won't cut it. Age, date difference, GPA, fuel cost, time-to-decimal, password strength — pick a tool and you're one click from your answer.
speed Loads in under a second
Every tool is plain HTML + JavaScript with the calculation logic compiled in. No spinner, no "verifying browser" splash, no five-second wait while ads load. Hit the page, fill the form, get the answer. Slow tools waste your time and ours.
devices Works on every device
Responsive design tested down to a 320px-wide phone screen. The input fields use native number/date keyboards on iOS and Android, the calculate button is thumb-sized, and the result still reads big and bold on the smallest screen. No app to download, ever.
sentiment_satisfied No funny business
No newsletter pop-ups, no "create an account to see the answer", no fake countdown, no fake stock counter, no upsell. Two ad slots per page (clearly labelled as Advertisement) keep the site free — that's the whole business model.
Interpretation guide
Acceptable voltage drop:
| Guideline | Limit |
|---|---|
| Branch circuit | <= 3% recommended |
| Feeder + branch | <= 5% total |
| Effect of long runs | More drop, may need larger wire |
| Effect of higher current | Proportionally more drop |
Formula & methodology
Formula: Vdrop = 2 x L x I x R / 1000 (single phase); % drop = Vdrop / Vsource x 100
Voltage drop is the loss along a conductor due to its resistance. The calculator multiplies the one-way distance by two (out and back for single phase), the current, and the wire's resistance per length to get the volts lost, then expresses it as a percentage of source voltage. Long runs and high current increase drop; upsizing the conductor (lower AWG number) reduces it. Codes typically recommend keeping drop at or below 3% on branch circuits.