Electrician Exam Calculator: What's Allowed (2026)

Most electrician exams allow a basic non-programmable calculator, and if you're not bringing one, you're leaving points on the table. Load calculations, voltage drop, and motor sizing questions all involve multi-step math that's slow and error-prone without a calculator. Here's exactly what's allowed, which model to use, and the six calculation types you need to practice before exam day.

What's Allowed

PSI exams (most states): Basic scientific or four-function calculator permitted. Must be non-programmable, non-graphing, and silent. No phone calculators. The proctor may inspect your calculator before the exam starts.

Pearson VUE exams (Florida, some others): Same rules. Basic non-programmable calculator allowed. Some Pearson VUE test centers also provide an on-screen calculator, but relying on it slows you down significantly.

Prometric exams: Calculator policy varies. Check with your state board, but most permit the same basic calculator rules.

What's NOT allowed:

• Programmable calculators (TI-84, HP 50g)
• Graphing calculators
• Calculators with unit-conversion or formula-storage features
• Phone calculators or tablet apps
• Printing calculators

Recommended Models

Texas Instruments TI-30X IIS is the standard recommendation for electrician exams. It has square root, percentage, and memory functions. Costs about $15. Button layout is intuitive and most exam prep instructors recommend this specific model.

Casio FX-115ES Plus has more functions than you need, but all are basic enough to pass inspection. Natural display makes fractions easier to read. About $18.

Sharp EL-531 is a budget-friendly alternative that gets the job done.

Avoid any calculator that has a QWERTY keyboard or a flip cover that could store notes. Those get confiscated on sight.

The 6 Calculations You Must Know Cold

1. Voltage Drop (NEC 210.19 Informational Note)

Formula: VD = (2 × K × I × D) / CM

• K = 12.9 for copper, 21.2 for aluminum
• I = current in amps
• D = one-way distance in feet
• CM = circular mils (from NEC Table 8 or Table 310.16)

The NEC recommends limiting voltage drop to 3% for branch circuits and 5% cumulative from source to load. Practice target: Solve a voltage drop problem in under 90 seconds with your calculator open to Table 310.16.

2. Load Calculations, Standard Method (NEC Article 220, Part III)

For a dwelling unit, the key numbers are 3 VA/sq ft for general lighting, 1,500 VA for each small appliance circuit (minimum two required), and 1,500 VA for the laundry circuit. Demand factors apply: first 3,000 VA at 100%, remainder at 35%.

Practice target: Calculate the minimum service size for a 2,000 sq ft home in about 3 minutes with Article 220 open.

3. Conductor Ampacity with Correction Factors (NEC Table 310.16)

Formula: Adjusted ampacity = Table value × temperature correction factor × adjustment factor

Temperature correction factors are in Table 310.15(B)(1). Bundling adjustment factors for more than 3 current-carrying conductors are in Table 310.15(C)(1). This is a two-multiplication problem once you've looked up the base values.

Practice target: Given wire gauge, insulation type, ambient temp, and conductor count, find adjusted ampacity in under 2 minutes.

4. Motor Branch Circuit Sizing (NEC Article 430)

The four steps: find FLA from Tables 430.247-430.250 (not the nameplate), size the conductor at FLA × 1.25 per NEC 430.22, size the OCPD at FLA × 2.5 for inverse-time breakers per Table 430.52, and set overload protection at FLA × 1.15 for motors with a 1.15+ service factor per 430.32.

Practice target: Given motor HP and voltage, size all four components without looking up the formula steps.

5. Transformer kVA and Current

Single-phase: I = kVA × 1,000 / V

Three-phase: I = kVA × 1,000 / (V × 1.732)

Apply the formula once for primary voltage and once for secondary voltage to get both currents. Practice target: Size a 75 kVA, 480V/208V three-phase transformer in under 60 seconds.

6. Conduit Fill (NEC Chapter 9, Tables 4 and 5)

Total wire area divided by conduit area must be 40% or less for three or more conductors (53% for one conductor, 31% for two). The math is simple percentages, but the speed comes from knowing which table to go to: Table 5 for wire cross-sectional area by gauge and insulation type, Table 4 for conduit interior area by type and trade size.

How to Practice

Time yourself on 10 voltage drop problems with the actual formula and a stopwatch. If you can't get under 90 seconds per problem consistently, your NEC lookup flow needs work, not your arithmetic.

Practice your tab system alongside your calculator. Calculator speed means nothing if you're hunting for Table 310.16 each time. Tab every table you'll reference for calculations.

Know when not to reach for it. For a question like "what is the minimum conductor size for a 20A circuit?", picking up your calculator wastes time. Know the standard sizes cold: 14 AWG/15A, 12 AWG/20A, 10 AWG/30A, 8 AWG/40A, 6 AWG/55A.

Related Reading

• NEC Article 220: Load Calculations with Worked Examples
• NEC Table 310.16: Wire Sizing and Ampacity Guide
• Electrician Exam Math: Complete Formula Guide
• What to Bring to the Electrician Exam
• NEC Article 430: Motors