How to Use the TI-84 Calculator Online — Complete Beginner's Guide

By Miqdad Qaisrani | Updated July 25, 2026

Open the free TI‑84 calculator →

This guide is written for someone who has never used a TI-84 before. No prior experience is assumed. You will learn what every important key does, how the screen works, how to enter expressions, how to clear mistakes, and how to use the shift keys. By the end, you will be able to perform basic arithmetic, use variables, navigate the MATH menu, and avoid the most common beginner mistakes. Once you master the basics here, the main Calc84 page has the full interactive calculator to practice on.

Starting the calculator: what you see

When you open the online TI-84 calculator and press the Start button (or the onscreen ON key), you see a screen with space for 8 lines of text. At the top right of the screen, small text may show the current mode settings. At the bottom, a flashing rectangular cursor indicates where your next typed character will appear. If the screen is blank except for the cursor, the calculator is in the home screen — where most calculations happen.

The keypad below the screen has about 50 keys arranged in rows. Each key has up to three functions: the primary function (printed on the key itself), a secondary function (printed in blue or yellow above the key, accessed with the 2nd key), and an alpha character (printed in green or as a letter above the key, accessed with the ALPHA key). We will cover these shift keys in detail below.

The MODE button: Degree/Radian, Float/Fraction, and other settings

Press MODE (next to the 2nd key) to open the mode settings screen. This is worth checking before you start any serious work. The most important settings for a beginner are:

• Radian vs. Degree: This controls whether trigonometric functions use radians or degrees. The default is Radian. If you are typing sin(30) and expecting 0.5, switch to Degree mode. Arrow down to the "Radian Degree" line, arrow right to highlight "Degree," and press ENTER. The small indicator in the top-right corner of the home screen will show DEGREE instead of RADIAN.
• Float vs. fixed decimal: "Float" means the calculator shows as many decimal places as needed. For example, 1/3 displays as .3333333333 (10 digits). If you select a fixed decimal mode (like "2"), results display with exactly 2 decimal places. Most students keep this on Float.
• Func / Par / Pol / Seq: This controls graphing mode. Keep it on "Func" (function) unless you are doing parametric, polar, or sequence graphing. We cover these modes in the graphing engine page.

To exit the MODE screen, press 2nd then MODE (which selects the QUIT command printed above the MODE key). This returns you to the home screen.

Basic arithmetic: entering expressions and the ENTER key

The TI-84 uses algebraic entry, which means you type expressions the same way you write them. For example, to calculate 15 + 27, type 15 + 27 and press ENTER. The screen shows:

15+27
         42

The expression stays on the left, and the answer appears on the right. If you want to reuse that answer in the next calculation, use the 2nd + (-) key combination, which calls up the ANS variable. For example, typing ANS * 3 and pressing ENTER multiplies 42 by 3 and gives 126.

Parentheses work as you would expect. To calculate (3 + 5) / 2, type (3 + 5) / 2 and press ENTER. The calculator evaluates expressions using the standard order of operations (PEMDAS: parentheses, exponents, multiplication/division, addition/subtraction). If you forget to close a parenthesis, the calculator may show an ERR: SYNTAX message — we cover how to fix that in the common mistakes section below.

Clearing: CLEAR, DEL, and 2nd+QUIT

Three different keys handle clearing and deleting, and mixing them up is a common source of confusion for beginners:

• CLEAR — Clears the current line of input from the home screen. If you have typed a long expression and want to start over, press CLEAR. It does not erase your previous calculation history — those stay visible above the current line.
• DEL — Deletes the character under (to the right of) the cursor. This is like the Delete key on a computer keyboard. Useful for fixing a typo in the middle of an expression — arrow over to the mistake and press DEL.
• 2nd + MODE (QUIT) — Exits whatever menu or screen you are on and returns you to the home screen. This is the "get me out of here" command. If you find yourself on a screen you did not intend to open (the Y= editor, the STAT lists, the MODE screen), press 2nd + QUIT to return home.

A practical example: if you accidentally press Y= and see the function editor, do not panic. Press 2nd + MODE to quit back to the home screen. If you see a menu you did not mean to open, the CLEAR key often (but not always) backs out one level.

The 2nd and ALPHA keys: how shift keys work

The 2nd key and ALPHA key are modifier keys — they change what happens when you press the next key. Think of them like Shift and Ctrl on a computer keyboard.

• The 2nd key (secondary functions): Every key has a secondary function printed in blue or yellow above the key. For example, the MODE key also has "QUIT" printed above it. To activate QUIT, press 2nd (notice the cursor changes to an upward-pointing arrow), then press MODE. Common 2nd functions include: 2nd + 0 (CATALOG — a list of every function), 2nd + 1 (L1 — list 1 for statistics), 2nd + x² (√ — square root), and 2nd + ^ (π — the constant pi).
• The ALPHA key (letters): Every key also has a letter printed in green above it. To type the letter A, press ALPHA then the MATH key (which has "A" printed above it). To type multiple letters in a row (like STO for "store"), press 2nd + ALPHA (A-LOCK) to lock alpha mode, then type each letter. Press ALPHA again to exit alpha lock.

The TI-84 keypad rewards memorisation: the more 2nd and ALPHA functions you internalise, the faster you get. But you do not need to memorise them all up front. The CATALOG (2nd + 0) lists every function alphabetically, and you can scroll through it at any time.

Memory: STO> (store) and using variables

The TI-84 has 27 built-in variables (letters A through Z plus θ) that can store numbers. To store a value, type the number, press STO› (the key just above the ON key, on the left side), then press the ALPHA key followed by the letter you want to use, then ENTER.

For example, to store the value 5 into variable A:

1. Type 5
2. Press STO›
3. Press ALPHA then MATH (the key with "A" above it)
4. Press ENTER

The screen shows: 5→A

Now whenever you use A in an expression — for example, A * 3 — the calculator substitutes 5. Variables persist until you overwrite them or clear memory (via 2nd + + → 2:Mem Mgmt/Del).

The variables X, Y, and θ are special: X is the independent variable for graphing, Y is typically used as the dependent variable, and θ is used in polar mode. You can still store numbers in them, but keep in mind their graphing-related roles.

The MATH menu: fractions, roots, absolute value, and more

Press the MATH key (just below the ALPHA key) to open the MATH menu, which has three submenus labeled MATH, NUM (numeric), and PROB (probability). This is where many of the calculator's most useful functions live:

• MATH submenu (default):
  • 1: ›Frac — Converts a decimal to a fraction. Type .75, press MATH, select 1: ›Frac, press ENTER. Result: 3/4.
  • 2: ›Dec — Converts a fraction to a decimal. Type 3/4, press MATH, 2: ›Dec, ENTER. Result: .75.
  • 3: ³√( — Cube root. Type ³√(27) and get 3.
  • 4: ˣ√( — nth root. For the fourth root of 16, type 4ˣ√16 and get 2.
  • A: logBASE( — Logarithm with a custom base. The syntax is logBASE(value, base), so for log base 2 of 8 you type logBASE(8,2) and get 3.
• NUM submenu (arrow right once):
  • 1: abs( — Absolute value.
  • 2: round( — Round to a specified number of decimal places. round(3.14159, 2) gives 3.14.
  • 3: iPart( / 4: fPart( — Integer part and fractional part of a number.
  • 8: lcm( / 9: gcd( — Least common multiple and greatest common divisor.
• PROB submenu (arrow right twice):
  • 1: rand — Random number between 0 and 1.
  • 2: nPr / 3: nCr — Permutations (order matters) and combinations (order does not).
  • 4: ! — Factorial. 5! = 120.

Keyboard shortcuts reference table

On the physical TI-84, every key is a physical button. On the online calculator, you can use either the onscreen keys or your computer keyboard. Here are the most useful keyboard shortcuts:

Using keyboard shortcuts is significantly faster than clicking onscreen buttons, especially for data entry or long calculations. Once you learn the shortcuts, you can drive the calculator without taking your hands off the keyboard.

Common mistakes beginners make and how to fix them

Every TI-84 user makes these mistakes at least once. Here is what goes wrong and how to recover:

• ERR: SYNTAX — This appears when your expression has a formatting error, such as a missing parenthesis or an operator in the wrong place. The calculator shows "1:Quit" and "2:Goto." Select 2: Goto to jump to the location of the error, then fix the expression and try again.
• ERR: DOMAIN — You asked for something that is mathematically impossible, like the square root of a negative number (in Real mode) or the logarithm of a negative number. Check your input.
• ERR: DIM MISMATCH — You tried to perform an operation on lists or matrices of incompatible sizes. This happens most often in statistics — check that your lists have the same number of elements.
• Forgetting to close parentheses: The TI-84 auto-closes all open parentheses at the end of an expression when you press ENTER, but this can produce unexpected results in complex expressions. It is safer to close them explicitly.
• Being in the wrong MODE: You type sin(30) expecting 0.5, but get -0.988. You are in Radian mode. Press MODE, switch to Degree, and try again.
• Graph not showing: You pressed GRAPH but see a blank screen. Either: (a) no functions are turned on in the Y= editor (the = sign must be highlighted), or (b) the WINDOW is zoomed into an empty area. Press ZOOM then 6: ZStandard to reset.
• Screen frozen or unresponsive: On the physical TI-84, you would remove a battery. On the online calculator, refresh the browser tab — your entries are saved to local storage automatically, so you will not lose work.

Frequently asked questions from beginners

The TI-84 looks intimidating at first — 50+ keys, multiple modes, and three functions per key. But you do not need to learn everything at once. Start with basic arithmetic and the ENTER key. Add the MATH menu when you need fractions and roots. Explore variables with STO› when you want to reuse numbers. The free online TI-84 calculator at Calc84 lets you practice all of this without the anxiety of making mistakes on an expensive physical device. Open it now and try typing your first expression.

Page last updated: July 25, 2026

Miqdad Qaisrani

Creator of Calc84

Miqdad is a full-stack engineer and cybersecurity student specializing in educational technology (EdTech). He built Calc84's online TI-84 interface so that anyone can learn the TI-84 keypad for free, from scratch, at their own pace.

About the Developer Contact & Support