The master Calculations portion: items, method, worked examples

A note on numbers: every section and table number on this page is 2023 numbering. Some may differ in the 2026 NEC, so confirm each one in your own book before you rely on it.

What the portion covers

• Items: 33 on screen, 30 of them scored. The bulletin says the time for the non-scored items is already included in the time allowed, so answer every item.
• Time: 170 minutes, counting down at the top of the screen. You can go back to any item and change your answer while time remains.
• Passing: 70% on this portion, scored separately from NEC Knowledge (75 items in 150 minutes).
• Reading rules: conductors are copper unless the question says otherwise, and you do not apply code exceptions or optional calculation methods unless the question directs you to.
• Book and calculator: a soft-bound 2026 NEC with publisher tabs only, and a silent, battery-operated, non-programmable calculator with no paper tape and no alphabet keyboard. Our calculator post covers what to look for.
• Fee: $78 covers both portions, and the retake for one portion or both is $78.

Against the journeyman Calculations portion (26 items in 110 minutes), the master portion has 7 more items and 60 more minutes.

Items by subject area

Scored items in the Calculations portion, paraphrased from the bulletin's outline. The master exam outline puts these beside the NEC Knowledge counts.

Services and motors carry 14 of the 30 scored items. Add feeders and branch circuits, and four areas carry 21. Compared with the journeyman portion, services goes from 4 items to 8 and motors from 2 to 6, so load and motor work is where the master portion gets longer.

Method by calculation type

1. Service and dwelling loads. The load-calculation rules are Article 220 in the 2023 NEC; find where your 2026 book puts them. Use the standard method (Part III in 2023) unless the question names the optional method (Part IV), since the bulletin rules out optional calculation methods unless a question directs you to them. Work the loads in the order the question lists them, apply each demand factor only from the table the method points to, then divide total volt-amperes by the voltage, or by voltage × 1.732 for three-phase. Service-entrance conductor sizing starts at 230.42.
2. Feeders. Take 125% of the continuous load plus the noncontinuous load as the minimum for the conductor (215.2(A)(1)) and the overcurrent device (215.3), then go to a standard rating in 240.6(A). A feeder that supplies motors follows 430.24 for its conductors and 430.62 for its protection.
3. Motors and generators. Use table current, not the nameplate, under 430.6(A)(1): Table 430.250 for three-phase and Table 430.248 for single-phase. Branch conductors come from 430.22, the short-circuit and ground-fault device from 430.52 and Table 430.52, and overloads from the nameplate under 430.32. With exceptions off, take the largest standard device not over the result. Generator output conductors start at 445.13. Our motor calculations guide walks all five motor outputs.
4. Transformers and separately derived systems. Convert kVA to current on each side, and check the arithmetic with the transformer calculator. Protection is in 450.3 (Table 450.3(B) for 1000 volts and less), secondary conductors in 240.21(C) and grounding in 250.30.
5. Conductors. Find base ampacity in Table 310.16 at the column the terminals allow under 110.14(C), then apply the ambient correction (Table 310.15(B)(1)) and the adjustment for more than three current-carrying conductors (Table 310.15(C)(1)). The conductor ampacity guide works one through.
6. Voltage drop. The NEC treats voltage drop as a design target in informational notes, so the question gives you the percentage. Circular mils = 2 × K × I × L ÷ allowed drop for single-phase; use 1.732 in place of 2 for three-phase. K is about 12.9 for copper, and Chapter 9 Table 8 gives circular mils by size. See the voltage drop guide and try numbers in the voltage drop calculator.
7. Grounding and bonding conductors. Size equipment grounding conductors from Table 250.122 by the overcurrent device rating, and grounding electrode conductors from Table 250.66 by the size of the service conductors.
8. The single-item areas. Raceway fill uses Chapter 9 Tables 1, 4 and 5. Air conditioning motor-compressors are Article 440, with conductors sized from rated-load current under 440.32. EV charger loads are treated as continuous under 625.41. RV park and mobile home park loads have their own demand rules in Articles 551 and 550. A motor disconnect is rated from table current under 430.110.

Worked example 1: a commercial feeder load

These are invented numbers, written for practice. A 208Y/120 volt, three-phase feeder supplies 36,000 VA of continuous lighting load and 15,000 VA of noncontinuous equipment load. What is the minimum feeder overcurrent device, and what copper conductor goes with it?

• Calculated load: 36,000 × 1.25 = 45,000 VA. Add the noncontinuous 15,000 VA for 60,000 VA.
• Current: 60,000 ÷ (208 × 1.732) = 60,000 ÷ 360.3, which is about 166.5 A.
• Device: the smallest standard rating in 240.6(A) at or above 166.5 A is 175 A.
• Conductor: the circuit is over 100 A, so the 75°C column applies under 110.14(C). In Table 310.16, 1/0 AWG copper carries 150 A, too small, and 2/0 AWG carries 175 A, so 2/0 AWG copper is the answer.

Read whether the question wants the calculated amperes, the device or the conductor. Each is a different answer choice.

Worked example 2: two motors on one feeder

A 460 volt, three-phase feeder supplies a 20 horsepower motor and a 7.5 horsepower motor, each on its own inverse-time breaker. Find each branch breaker, then the feeder conductor ampacity and the feeder breaker.

• Table current (Table 430.250): 27 A for 20 horsepower, 11 A for 7.5 horsepower.
• Branch conductors (430.22): 27 × 1.25 = 33.75 A and 11 × 1.25 = 13.75 A.
• Branch breakers (Table 430.52, 250% for inverse-time): 27 × 2.5 = 67.5 A, so the largest standard size not over it is 60 A. 11 × 2.5 = 27.5 A, so 25 A. Exceptions are off unless the question directs you to one.
• Feeder conductors (430.24): 125% of the largest motor plus the other: 33.75 + 11 = 44.75 A. At the 60°C column, 6 AWG copper (55 A) is the smallest that carries it.
• Feeder breaker (430.62(A)): the largest branch device plus the table current of the other motor: 60 + 11 = 71 A. The largest standard size not over 71 A is 70 A.

The common miss is adding 125% to every motor on the feeder. Only the largest motor gets it.

Pacing

170 minutes for 33 items is about 5 minutes an item, by our own division, against about 4 for journeyman. The extra time points to longer, multi-step items, so spend it on the steps, not on rereading.

1. First pass: answer every item you can finish in a few minutes, theory and single-lookup items first.
2. Mark the long ones: a multi-step load or feeder calculation goes to the end of your first pass. You can return to it while time remains.
3. Label your notepad: for any motor item, write the table current and the nameplate current at the top, labeled, before you open the book.
4. Last pass: check units and whether the question asked for a calculated value or a standard size, then make sure every item has an answer.

Practice the 170 minutes as one block, on its own, so the clock feels familiar on the day.

Check your calculation skills

Take the free 10-question check to see which master subject areas cost you points. It needs no signup, and every answer is explained. Then run a timed mini-mock at the published exam's pace, scored by topic.

FAQ

How many questions are on the Texas master Calculations portion?

33 items, 3 of them non-scored, so 30 count for your score. The NEC Knowledge portion is separate, with 75 items.

How long is the master Calculations portion, and what do I need to pass?

170 minutes, and 70% to pass. The portion is scored on its own, and time left over does not carry into NEC Knowledge.

Which calculations carry the most items?

Services, service equipment and separately derived systems carry 8 of the 30 scored items, and motors and generators carry 6. Branch circuits and conductors carry 4 and feeders 3.

Do I use exceptions and optional methods on the master exam?

Not unless the question directs you to. The bulletin says so for every Texas electrician exam, and it also says conductors are copper unless the question notes otherwise.

Is the journeyman Calculations portion the same?

The method is the same, with fewer items: 26 items in 110 minutes, 2 of them non-scored. Our journeyman Calculations guide covers it with its own worked examples.

Where do our practice questions come from?

Every question is original and written to PSI's published content outline for the master exam. Each explanation cites the NEC article, section or table it relies on, by number only.

Not affiliated with or endorsed by TDLR, PSI or NFPA. NEC and National Electrical Code are registered trademarks of NFPA.

Sources

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• Candidate Information Bulletin, Texas electricians (updated 9/15/2026), PSI for the Texas Department of Licensing and Regulation. Checked 7 Nov 2026.
• Electrician exam information, Texas Department of Licensing and Regulation. Checked 7 Nov 2026.
• NFPA 70, National Electrical Code (2026 edition), NFPA. Free read-only access with an account. Checked 7 Nov 2026.