Voltage drop calculator and exam trainer
Enter your numbers and see every step: the drop in volts and percent, and the smallest wire that keeps you under 3%. Then practice exam-style questions below.
On the Texas exam you get about 4 min 14 s per Calculations question (26 questions in 110 minutes). The trainer below times you against that pace.
Calculator
Circular-mil areas are the conductor properties in NEC Chapter 9, Table 8. K values are the ones most exam questions use; if a question gives you a different K, use theirs.
Try it like the exam
0:00New question every time. Answer, see the working, and watch your streak.
Ready for the whole Calculations portion?
Voltage drop is one of the question types on the Texas Calculations portion. Our free 20-question diagnostic covers all of them on the 2026 NEC and shows which areas cost you points.
Take the free diagnostic See the full exam packMore free trainers: Amps, kW and kVA trainer · Box fill trainer · Conduit fill trainer