Calculator Rules for the Texas Electrician Exam

Every Texas electrician exam has calculations, and you bring your own calculator. PSI’s rule is short, but it rules out more than people expect. This guide explains the rule, how to pick a calculator that clearly passes it, and how to use it so it saves time instead of costing it.

Key facts

• PSI allows only non-programmable calculators.
• The calculator must be silent and battery-operated.
• It must have no paper tape printing.
• It must have no keyboard containing the alphabet.
• Phones, smart watches and every other electronic device go into secure storage before you enter the room.
• PSI gives you an electronic notepad. The bulletin does not mention an on-screen calculator.

The rule, piece by piece

The PSI Candidate Information Bulletin lists the calculator rule under Security Procedures. Here is what each part means in practice.

PSI requirement	What it rules out
Non-programmable	Graphing calculators, calculators that store programs or formulas, anything you can load software onto
Silent	Calculators with key beeps or sound you cannot turn off
Battery-operated	Plug-in desk calculators. Solar-only models are a gray area, see below
No paper tape printing	Printing adding machines
No keyboard containing the alphabet	Calculators with a letter keyboard, which also catches most programmable and algebra models

PSI does not publish a list of approved models in the bulletin. It sets the rules and checks items at check-in, where candidates are asked whether they have prohibited items. An item found at check-in has to go into storage or back to your car. Any prohibited item found in the exam room gets your results invalidated.

Gray areas TDLR and PSI do not settle

• Solar-only calculators. The rule says battery-operated. TDLR and PSI do not say whether a calculator that runs only on solar power is accepted. A model with a battery, or solar with battery backup, avoids the question.
• Letters printed on keys. Some scientific calculators print small letters above certain keys for storing variables. PSI’s wording is about a keyboard containing the alphabet. PSI does not say whether a few variable letters count. If you want zero risk, choose a model without them.
• A spare calculator. The bulletin does not say whether you may bring a second calculator. Put a fresh battery in your one calculator the week before instead.

What to look for when you buy

A basic scientific calculator covers everything on the exam. You want:

• Square root and x² keys. You need √3 for three-phase problems and squares for some theory questions.
• Parentheses. They let you enter a formula in one line without writing down partial results.
• A memory key (M+, MR or STO). Store 1.732 once and recall it.
• A two-line or clear display, so you can see what you typed before you press equals.
• A battery you can replace, and a fresh one before exam day.

You do not need fraction modes, statistics, unit conversions or anything programmable. Each extra feature is one more thing a proctor might question.

Use it fast: keystroke habits that prevent errors

Most calculator mistakes on electrical exams are order-of-operations slips, not wrong formulas.

Three-phase current. Current equals power divided by (voltage × 1.732). For a 50,000 W load at 480 V:

• Right: 50,000 ÷ (480 × 1.732) = about 60.1 A
• Wrong: 50,000 ÷ 480 × 1.732 = about 180 A, because the calculator divides first and then multiplies

Use parentheses, or divide twice: 50,000 ÷ 480 ÷ 1.732.

Single-phase voltage drop. Voltage drop equals 2 × K × I × L ÷ circular mils. For copper (K about 12.9), 40 A, 150 ft, 10 AWG (10,380 circular mils):

• 2 × 12.9 × 40 × 150 ÷ 10,380 = about 14.9 V

Multiply everything on top first, then divide once at the end. That keeps one chain of keystrokes and no rounding along the way.

Other habits:

• Keep full precision until the last step. Round only the final answer, and round the way the question or the code says.
• Clear the calculator fully between problems. A leftover value in memory can silently ruin the next answer.
• Write the result of each step on the electronic notepad for multi-step problems such as dwelling loads, so a slip does not force you to start over.
• Estimate first. If a 20 A branch circuit problem gives you 180 A, you have pressed something wrong.

Practice with the exact calculator you will bring

Buy your exam calculator early and use it for every drill on this site. Our three-phase power, voltage drop, transformer current and power factor and efficiency drills are the most keystroke-heavy, so they are good for building habits. The worked steps show each operation in order, so you can check where your keystrokes went wrong.

When you can do our Ohm’s law and motor full-load current problems without looking at the keys, move on to timed sets on the journeyman, master or residential wireman practice test. The formula sheet lists every formula we use.

On exam day

Your calculator is one of the few things allowed in the room with you, along with your compliant NEC. Bring it out of its case if the case has notes or papers in it. Everything else, including your phone, watch and wallet, goes into storage. See exam day at PSI for the full check-in list, and open-book NEC rules and tabs for the book rules.

TexasElectricianExam is an independent study site, not affiliated with TDLR, PSI or NFPA. Check the current PSI bulletin before you test.