Voltage Drop Calculator
Find the long runs before they find your margin.
Check voltage drop on feeders and branch circuits while you price, not after award. Enter voltage, phase, conductor, parallel sets, length, and load; get volts dropped, percent drop, pass or fail against the NEC informational-note guidance (3% feeder or branch, 5% combined), and the smallest conductor size that passes.
Features
- Single-circuit calculator with the full calculation shown
- Batch tab checks up to 50 circuits at once
- Chains branch circuits to their feeder for the combined 5% check
- Suggested minimum conductor size for voltage drop, plus the longest run that passes
- Copper and aluminum, single and three phase, parallel sets
- Conductor table from #14 AWG to 2,000 kcmil
- Editable K values and limits for stricter specs
Uses the standard K-factor estimating formulas. It checks voltage drop only; confirm ampacity, conduit fill, and code minimums separately.
Questions
How do I get the files?
Checkout runs through Gumroad. Right after you pay, you get a download link on screen and by email. Nothing ships.
Do they work in Google Sheets?
Yes. Upload the .xlsx to Google Drive and open it with Google Sheets. Formulas, dropdowns, and colors carry over. No macros are used anywhere, so there's nothing to enable.
Are the labor units and rates filled in?
No, and on purpose. Every rate, factor, and markup is a clearly labeled placeholder you replace with your own. Your numbers stay yours.
What if something doesn't work?
Email helloscottcox@gmail.com and I'll fix it or make it right.
Is this engineering or legal advice?
No. These are estimating tools. You're responsible for verifying quantities, pricing, labor, and code compliance.