Which calculator to buy for the FE exam: the short answer
- Get the TI-36X Pro if you came up on TI calculators through school. At about $22 it handles complex numbers and matrix work up to 3×3, with linear systems up to 3 unknowns.
- Choose the Casio fx-991EX for the better display and the faster processor. It goes to 4×4 matrices and 4 unknowns where the TI stops at 3×3 and 3, at about $25.
- FE Electrical and Computer candidates get a real edge from the Casio: the 4×4 matrices and faster numeric integration suit heavy AC circuit analysis. For FE Civil and FE Mechanical, either model is fine.
- NCEES approves only model names containing TI-30X, TI-36X, fx-115 or fx-991, plus the HP 33s and HP 35s. Anything else gets confiscated at the Pearson VUE desk, and you solve 110 engineering problems with pencil arithmetic.
- Buy the TI-36X Pro or the Casio fx-991EX today and use it for every single practice problem until exam day. The one you know cold beats the one with the better spec sheet that you are still figuring out on test morning.
The Approved List (Complete)
NCEES permits exactly these calculator models on the FE exam. No exceptions, and no "but it's basically the same as..."
Texas Instruments: Any calculator with "TI-30X" or "TI-36X" in the model name. This includes the TI-30X IIS, TI-30X IIB, TI-30XS MultiView, TI-36X Pro, and the newer TI-36X Pro (MathPrint edition).
Casio: Any calculator with "fx-115" or "fx-991" in the model name. This includes the fx-115ES Plus, fx-115ES Plus 2nd Edition, fx-991EX (ClassWiz), and the newer fx-991CW.
Hewlett-Packard: HP 33s and HP 35s only. These use RPN (Reverse Polish Notation) input, which is unusual. Unless you're already fluent in RPN, skip these.
If your calculator's model name doesn't contain one of those exact strings, it's not allowed. The Pearson VUE proctor will check, and they will confiscate unapproved calculators. You'll then solve 110 engineering problems with pencil arithmetic. Don't let this happen to you.
TI-36X Pro: The Workhorse
The TI-36X Pro is the default recommendation in most FE prep courses, and for good reason. It's the most capable calculator on the approved list while still being intuitive for anyone who grew up on TI calculators.
What it does well: Complex number arithmetic (critical for FE Electrical candidates doing AC circuit analysis). Matrix operations (up to 3×3). Systems of linear equations (up to 3 unknowns). Definite integrals and derivatives (numeric). Unit conversions. Statistical distributions. The MathPrint display shows expressions as you'd write them on paper (fractions look like fractions, exponents are superscripted), which reduces input errors on multi-step calculations.
What to watch for: The menu navigation takes getting used to. Functions like complex number mode and matrix entry are buried in menus that require multiple keypresses. On exam day, you need these to be reflexive, not something you're figuring out. Spend your first week of study just learning the calculator's menus by working through problems that use each function.
Price: ~$20–$25.
Casio fx-991EX (ClassWiz): The Dark Horse
The Casio fx-991EX is less commonly recommended in US-centric prep courses, but among candidates who've used both, it has a devoted following. The newer fx-991CW variant offers the same functionality with a slightly updated interface.
What it does well: Higher-resolution display (192×63 pixels vs. TI's lower resolution) makes complex expressions more readable. Faster processor, noticeable on numeric integration and equation solving. Spreadsheet mode (up to 5 columns × 45 rows) for tabular calculations. QR code feature (not useful for the exam, but handy during study). Matrix operations up to 4×4 (vs. TI's 3×3). Complex number arithmetic. Systems of equations up to 4 unknowns (vs. TI's 3).
What to watch for: If you've spent years on TI calculators, the Casio key layout will feel foreign. The mode-switching system (you select a mode for the type of calculation) is different from TI's menu-driven approach. The learning curve isn't steep, but it exists. Give yourself a week to adjust before committing.
Price: ~$20–$30.
Head-to-Head: What Matters for the FE
| Feature | TI-36X Pro | Casio fx-991EX |
|---|---|---|
| Complex numbers | Yes | Yes |
| Matrix size | 3×3 | 4×4 |
| System of equations | 3 unknowns | 4 unknowns |
| Numeric integration | Yes | Yes (faster) |
| Display quality | Good | Better |
| US familiarity | High (most US students used TI) | Lower |
| Spreadsheet mode | No | Yes |
| Price | ~$22 | ~$25 |
For FE Civil and FE Mechanical candidates: either works. Your exam is calculation-heavy but rarely requires matrices larger than 3×3 or systems beyond 3 unknowns. The TI-36X Pro's familiarity advantage likely outweighs the Casio's spec sheet advantages.
For FE Electrical and Computer candidates: the Casio fx-991EX has a meaningful edge. The 4×4 matrix capability and faster numeric integration make it better suited for the heavy AC circuit analysis and linear systems work on the electrical exam. If you're comfortable with Casio's interface (or willing to invest a week learning it), it's the stronger choice for ECE.
The Only Rule That Actually Matters
Pick one. Buy it today. Use it for every single practice problem until exam day. The calculator you know cold is worth more than one with marginally better features that you're still figuring out on test morning. The TI-36X Pro and Casio fx-991EX are both excellent tools for the FE exam. The bad choice isn't picking the "wrong" one. It's showing up on exam day without having used your calculator for hundreds of practice problems.
For discipline-specific study guides that put these calculators to work: