How to Use a TI-84: The Basics

The TI-84 Plus and TI-84 Plus CE are graphing calculators, but most of what you actually do on one happens on the home screen, not the graph screen — typing expressions, reusing results, and storing values. Graphing itself is enough of its own workflow that it has a separate walkthrough; this one covers everything before that.

1. Enter and evaluate an expression

Type an expression the way you’d write it on paper. In MathPrint mode (the default on modern OS versions), fractions and exponents display stacked the way they’d look in a textbook — 3/4 renders as an actual fraction, not 3/4 flattened onto one line. The calculator also understands implicit multiplication, so 2(3+4) evaluates to 14 without needing a × between the 2 and the parenthesis. Press Enter to evaluate; the result appears right-aligned on the line below, with your original input still visible above it.

2. Reuse Ans and recall previous entries

Ans holds your last result and can be dropped into a new expression — type Ans (or just start typing an operator like *2, which inserts Ans automatically) to build on what you just calculated instead of retyping it.

2nd + Enter — labeled ENTRY above the Enter key — pastes your previous input line back onto the entry line, cursor and all, so you can edit one number and rerun it rather than typing the whole expression again. Press it a second time and it steps back one entry further, all the way through your recent history.

3. Store values in variables

STO-> followed by a letter (A through Z) stores whatever’s currently displayed into that variable. Type the same letter later — in any expression — and it drops in the stored value. This is what makes a problem with several steps manageable: compute an intermediate result once, store it as A, and reuse A two or three steps later without re-deriving or retyping it. Variables hold their value until you overwrite them or reset the calculator (see How to Reset a TI-84 if you need a clean slate).

4. Set your mode

MODE opens a full-screen grid of settings that stay in effect until you change them again — even after the calculator’s been off. The ones worth knowing early:

• Degree / Radian — wrong angle mode is the most common reason a trig answer looks completely wrong without throwing an error. See Degrees vs. Radians for when to use each.
• Float / 0123456789 — Float shows as many decimal places as fit; picking a number fixes every result to that many decimal places instead.
• Frac — some OS versions let you default answers to fraction form instead of decimal.
• Real / a+bi / re^θi — Real mode throws a domain error on something like √(-1); switching to a+bi returns a complex result instead.

Arrow down to any setting, arrow across to the option you want, and press Enter to select it.

Try it yourself

The TI-84 calculator on this site works the same way from your keyboard — type an expression in the Home tab and press Enter, use Ans the same way, and STO-> followed by a letter to store a value. Mode settings (angle unit, Frac/Dec) live in the strip above the display. For the buttons and symbols that don’t have an obvious key, see the TI-84 reference sheet.