Calculations Room
Calculations fail more candidates than any other section. On the Texas TDLR exam the Calculations part is now scored on its own, and the most recent published pass rate on it was 20.56 percent. The fix is not more formulas. It is a repeatable setup so a three-step problem never freezes you. Drill one type at a time.
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
- Learning a clean setup that works on every calculation type
- Working one calc type at a time until it is automatic
- Talking through where a number came from when you get stuck
What not to post
- Asking for the answer without the steps. The steps are the skill.
- Posting copied exam questions. Original scenarios only.
- Sharing personal details. Keep it about the math.
Answered questions in this room
How do I stop freezing when a calculation has three steps?
Freezing happens when you try to see the whole problem at once. Stop doing that. Use one fixed setup on every problem: name the problem, pick the formula or table, plug the values, run the math, check the rule. Write each line down. The page does the remembering so your head does not have to.
Is there a free electrician exam study group?
Yes. JourneymanIQ Study Hall is a free electrician exam prep community with state rooms, NEC skill rooms, codebook lookup drills, and staff-reviewed answers that cite article numbers instead of copying NEC text. It is free to read, privacy-first, and not an official test provider. The free diagnostic is your private next step.
Why do I keep failing the electrician exam calculations?
Usually it is not the math. It is setup and speed. Candidates who keep failing tend to memorize answers instead of a setup, freeze on multi-step problems, and run slow in the book. Fix the setup so every problem starts the same way, then build speed. That is what turns a repeat fail into a pass.
How do I study with other electrician exam candidates?
You do not need a scheduled group to study with other candidates. JourneymanIQ Study Hall gives you the same thing without the herding: rooms by state and skill, a daily drill in each, and staff answers to the questions other candidates keep asking. Work a room, run the daily drill, and bring your weak spots to the diagnostic.
What is the most missed part of the journeyman electrician exam?
Calculations, by a wide margin. On the Texas TDLR exam the Calculations part is scored on its own, and the most recent published pass rate on it was 20.56 percent, lower than the knowledge part. The math itself is not hard. It is setup under time pressure and slow code lookups that cost people the points.
How do I calculate three-phase voltage drop?
Three-phase voltage drop uses Vd = (1.732 x K x I x L) / circular mils. K is 12.9 for copper and 21.2 for aluminum, I is the operating current, and L is the one-way length in feet. The 1.732 handles the three-phase factor where a single-phase circuit would use 2. Pull circular mils from Chapter 9 Table 8.
What is a demand factor in electrical load calculations?
A demand factor lets you size a service or feeder for the load that actually runs at once, not every connected watt. Article 220 gives the factors. For dwelling general lighting, you take the first 3,000 VA at 100 percent and the remainder at 35 percent. The factors keep you from oversizing for loads that never all run together.
How many practice questions should I do before the exam?
Quality beats volume. Three hundred questions you fully understand, where you know why every wrong answer is wrong, teach more than a thousand you rush through. Use adaptive practice that surfaces your weak topics instead of random sets. Thirty minutes a night of targeted practice beats an hour of scattered drilling every time.
Room FAQ
What is the Calculations Room?
Calculations fail more candidates than any other section. On the Texas TDLR exam the Calculations part is now scored on its own, and the most recent published pass rate on it was 20.56 percent. The fix is not more formulas. It is a repeatable setup so a three-step problem never freezes you. Drill one type at a time.
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
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Quick back-and-forth with others studying this room. You post under a pseudonym. Be straight, cite article numbers, never copied code.
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