Texas TDLR Calculations Room
On the Texas TDLR exam the Calculations part is timed and scored on its own: 26 questions in 110 minutes, 70 percent to pass. A strong code score no longer carries a weak math score. The most recent published pass rate on this part was 20.56 percent, the lower of the two. Treat it as its own exam.
Last reviewed June 2026 · Staff Answer
A 120-volt branch circuit runs 70 feet one way on 12 AWG copper carrying 16 amps.
What is the approximate voltage drop? (K = 12.9, 12 AWG = 6530 cmils)
Pick an answer to see the work and why each wrong choice traps people.
What this room is for
- Understanding that calculations are now graded separately
- Prioritizing the calc types that show up most
- Building speed so 26 questions fit in 110 minutes
What not to post
- Asking for pasted NEC tables. Cite the article and table.
- Posting copied exam questions.
- Sharing personal or license details.
Answered questions in this room
I failed the TDLR Calculations part. What should I study first?
Start with your score report, not a textbook. The Calculations part is scored on its own now, so the report tells you which calc families cost you. Drill your bottom two first: usually some mix of conduit fill, box fill, dwelling load, and motors. Fix those before touching anything you already passed.
How many questions are on the TDLR Calculations part?
The Calculations part is 26 questions in 110 minutes, scored on its own at 70 percent to pass. It is separate from the NEC Knowledge part, which is 59 questions in 130 minutes. Since the split, a strong knowledge score no longer covers a weak calculations score, which is why this part fails the most people.
Why is the Texas TDLR calculations part scored separately now?
Since March 11, 2025 the TDLR Journeyman exam is two separately-scored parts: NEC Knowledge and Calculations. They are timed and graded on their own, and you need 70 percent on each. The practical effect is that a strong code score can no longer carry a weak math score, which is why the Calculations part now fails the most people.
Official sources
Room FAQ
What is the Texas TDLR Calculations Room?
On the Texas TDLR exam the Calculations part is timed and scored on its own: 26 questions in 110 minutes, 70 percent to pass. A strong code score no longer carries a weak math score. The most recent published pass rate on this part was 20.56 percent, the lower of the two. Treat it as its own exam.
What should I do first in this room?
Start with the daily drill. Pick an answer before reading the explanation, then read why the wrong choices trap candidates.
When should I take the full diagnostic?
Take the full diagnostic when you are not sure which NEC area is costing you points, or when the same miss shows up more than once.
Discussions
Loading discussions…
Live chat
Quick back-and-forth with others studying this room. You post under a pseudonym. Be straight, cite article numbers, never copied code.
Loading chat…
Messages are public to signed-in members and can be removed by moderators. Personal info is auto-stripped.
Want your own weak-topic map?
The rooms are free. When you want a plan built around your gaps, the diagnostic is 15 questions and no signup. It tells you which NEC sections to focus on, in priority order.
Run the full diagnostic