How to Calculate a Cube Root on a TI-84 Calculator

The cube root button isn't sitting on the keyboard waiting for you. That's the first thing that trips people up. Unlike the square root key — which has its own dedicated button — cube roots on the TI-84 are tucked away in a menu, and if you don't know where to look, you'll spend more time hunting than calculating.

This guide covers four different ways to find a cube root on the TI-84, from the quickest one-liner to the method that works for any nth root you'll ever need.

Don't have your physical device nearby? You can easily follow along using our free TI-84 Online Calculator or our TI-83 Plus Calculator tools right from your browser.

What Is a Cube Root?

The cube root of a number is the value that, when multiplied by itself three times, gives you that number.

So the cube root of 27 is 3, because 3 × 3 × 3 = 27.
Written mathematically: ∛27 = 3

Now, here's how to get the TI-84 to do that for you. Note: It helps to know your way around the interface, so if things feel confusing, referencing our TI-84 Plus CE button guide can help you locate specific keys.

Method 1: Use the MATH Menu (Easiest Way)

This is the most straightforward method and the one worth memorizing first.

Steps:

1. Press the MATH button (it's on the left side of the calculator, below the ALPHA key).
2. You'll see a list of options. Look for 4: ∛( — that's the cube root function.
3. Press 4 (or arrow down to it and press ENTER).
4. Type your number. For example: 27
5. Close the parenthesis with ).
6. Press ENTER.

Result: 3
That's it. ∛(27) gives you 3 instantly.

Try it with a messier number: ∛(50) gives you 3.684031499. The TI-84 handles decimals just fine — cube roots don't always come out clean.

A quick note on parentheses: The TI-84 opens a parenthesis automatically when you select the cube root function, but it won't close it for you. If you forget the closing parenthesis on a simple calculation it usually still works, but it's a good habit to close it — especially when you're nesting this inside a larger expression.

Method 2: Use the Exponent (^) Method

This one is useful when you're working with expressions that already involve exponents, or when you want to understand what's actually happening mathematically.

The cube root of x is the same as x raised to the power of (1/3).
∛x = x^(1/3)

Steps:

1. Type your number. Example: 27
2. Press the ^ key (caret/exponent key, located above the division key).
3. Type (1/3)
4. Press ENTER

So you type: 27^(1/3) → press ENTER
Result: 3

The parentheses around 1/3 matter here. If you type 27^1/3 without them, the calculator reads it as (27^1)/3, which gives you 9 — not what you want.

This method works for any root. Cube root is ^(1/3), fourth root is ^(1/4), fifth root is ^(1/5), and so on. Once you get comfortable with this, you rarely need to go hunting through menus again.

Method 3: Use the xth Root Function from the MATH Menu

The TI-84 also has a general "nth root" function, which is handy when you want to be explicit about which root you're taking — or when you're working with roots other than cube roots. If you have stale settings causing errors with these basic operations, consider doing a RAM reset to start fresh.

Steps:

1. Type the root index first. For a cube root, type 3
2. Press MATH
3. Select 5: x√ (it's right below the cube root option — press 5 or arrow to it).
4. Type your number. Example: 27
5. Press ENTER

So your screen shows: 3 x√ 27 → press ENTER
Result: 3

This method reads almost like plain English: "the 3rd root of 27." Some people find it easier to think about this way, especially when switching between different root types in the same problem set.

For a 5th root of 243, you'd type: 5 x√ 243 → ENTER → 3

Method 4: Cube Root of a Negative Number

This one catches a lot of people off guard, so it's worth its own section.

The cube root of a negative number is a real number — unlike square roots of negatives, which go into imaginary territory. The cube root of -27 is -3, because (-3) × (-3) × (-3) = -27.

The problem: The TI-84 sometimes returns an error or a complex number when you try to take the cube root of a negative value using the standard methods.

The fix:

To fix the complex number issue:

• Press MODE
• Arrow down to the line that shows REAL / a+bi / re^θi
• Make sure REAL is selected (arrow to it and press ENTER)
• Press 2ND → QUIT to exit

Now try your calculation again. The result should come back as -3.
Alternatively, you can work around the issue entirely by computing the cube root of the positive number and then applying the negative sign manually: -(∛(27)) → -3

Cube Root of a Fraction or Decimal

No special steps needed here — just plug it in.

• Example: Cube root of 0.125
  ∛(0.125) → ENTER → 0.5
  That works because 0.5 × 0.5 × 0.5 = 0.125.
• Example: Cube root of 3/8
  ∛(3/8) → ENTER → 0.9085602964
  Or if you want the fraction form, you can press MATH → 1: ►Frac after the result appears, though not all cube root answers convert to clean fractions.

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Common Mistakes to Avoid

• Forgetting parentheses in the exponent method. 27^1/3 is not the same as 27^(1/3). The first gives you 9, the second gives you 3. Always wrap the fraction in parentheses.
• Not closing the parenthesis in the MATH menu method. Works fine most of the time, but causes headaches inside larger expressions. Just close it.
• Getting a complex number for negative inputs. Check your MODE settings and switch to REAL if needed.
• Confusing cube root with cube. The cube root of 27 is 3. The cube of 27 is 19,683. Easy to mix up when you're moving fast! If you feel like your data lists are starting to get overwhelmed with old problems, flush your calculator memory regularly.

Quick Reference

Which Method Should You Use?

For most situations, the MATH menu method (Method 1) is the fastest. Two button presses and you're in.

If you're working with a formula that already uses exponents, the caret method (Method 2) keeps everything consistent and is easier to read back when you check your work.

The nth root function (Method 3) is worth knowing for when you move into fourth roots, fifth roots, or anything beyond cube roots — the same technique handles them all.

Negative numbers are the one edge case where you might need to adjust your approach, but once you've dealt with it once, you'll remember the fix. You can find more advanced statistical guides like finding a Z-score here too.

Final Thoughts

Cube roots on the TI-84 aren't hard — they're just not obvious at first. The calculator has the function, it just doesn't advertise it. Once you know to press MATH and look at options 4 and 5, you've basically solved the problem.

Practice it a few times before an exam so your hands remember where to go. The last thing you want is to spend two minutes hunting through menus when you could be solving the actual problem.