The cube root button does the opposite of cubing a number
A cube root is the number that, when multiplied by itself three times, gives you your starting number. If you cube 5 (meaning 5 × 5 × 5), you get 125. The cube root of 125 is 5. On a calculator, you are asking: "What number times itself three times equals this?"
Most calculators have a cube root function, but where it lives and how you access it depends on what type of calculator you own. A basic four-function calculator (the kind that only adds, subtracts, multiplies, and divides) will not have it. A scientific calculator almost always does.
Key Takeaways
- Scientific calculators have a cube root button, usually labeled with a symbol like ∛ or accessed through a menu; basic calculators do not.
- On most scientific calculators, you enter the number first, then press the cube root button or use the shift key to access it.
- If your calculator does not have a dedicated cube root button, you can use the exponent function to calculate it by raising the number to the power of 1/3.
- Phone calculator apps in scientific mode have cube root functions in the same places as physical scientific calculators.
- The order matters: enter the number, then the operation, not the other way around.
Finding the cube root button on a scientific calculator
Open your scientific calculator and look for a button labeled ∛x or ∛. This is the cube root symbol. On some calculators, especially older or simpler models, the cube root function is hidden under a shift key or second function key—usually labeled Shift, 2nd, or Alt. Check the top or bottom of your calculator for this key.
If you see a button labeled x√y or y√x, that is a root function that works for any root, including cube roots. You would use it differently than a dedicated cube root button, and the manual that came with your calculator will show you the exact order of steps.
If you cannot find either symbol, check the calculator's manual or search online for your specific model number plus "cube root." Manufacturers place these buttons in different spots, and the manual will tell you exactly where yours is.
The step-by-step process on most scientific calculators
The standard order is: enter your number, then press the cube root button. For example, to find the cube root of 64:
- Type 64
- Press the ∛ button (or Shift + the cube root button if it is a second function)
- Press Enter or =
- The answer appears: 4 (because 4 × 4 × 4 = 64)
If your calculator has a root function button instead of a dedicated cube root, you may need to enter the number, press the root button, then enter 3 to specify that you want the cube root. Again, your manual will show the exact sequence.
Using the exponent method if you do not have a cube root button
If your calculator has no cube root button at all, you can still find a cube root using the exponent function. Every cube root is the same as raising a number to the power of 1/3. So the cube root of 8 is the same as 8 to the power of 1/3.
Here is how to do it:
- Type your number (for example, 8)
- Press the exponent button, usually labeled ^, x^y, or **
- Type (1/3) — use parentheses if your calculator has them, or just type 0.333333 (the decimal form of 1/3)
- Press Enter or =
- The answer appears: 2 (because 2 × 2 × 2 = 8)
This method works on almost any calculator that has an exponent function, including phone calculator apps in scientific mode.
Using the cube root function on your phone
Your phone's built-in calculator app has a scientific mode that includes cube root. On iPhone, open the Calculator app, rotate your phone to landscape, and you will see the scientific calculator layout with a ∛ button or a root function. On Android, open your calculator app and look for a menu button (three dots or lines) that switches to scientific mode.
Once in scientific mode, follow the same steps as a physical scientific calculator: enter your number, press the cube root button, and press equals. If you cannot find the cube root button in scientific mode, use the exponent method instead—raise the number to the power of 1/3.
Common mistakes and how to avoid them
The most common error is pressing the cube root button before entering the number. Always enter the number first, then the operation. If you press cube root and nothing happens, your calculator is waiting for you to type the number.
Another mistake is confusing cube root with division by 3. The cube root of 27 is 3 (because 3 × 3 × 3 = 27), not 27 ÷ 3 = 9. They are completely different operations, so do not try to divide instead.
If you get a strange decimal answer when you expect a whole number, your calculator may be rounding. For example, the cube root of 10 is approximately 2.154, not a whole number. That is correct. But if you are looking for the cube root of 8 and get 2.0000001, that is just rounding error from the calculator—the answer is 2.
Frequently Asked Questions
What is the difference between square root and cube root?
A square root asks what number times itself twice equals your starting number. A cube root asks what number times itself three times equals your starting number. The square root of 9 is 3 (because 3 × 3 = 9). The cube root of 27 is 3 (because 3 × 3 × 3 = 27). They use different buttons on your calculator.
Can I find a cube root on a basic four-function calculator?
No. Basic calculators only add, subtract, multiply, and divide. You need a scientific calculator, either physical or the scientific mode on your phone. If you only have a basic calculator, you would have to guess and check by multiplying numbers together until you find the right answer.
Why would I ever need to use cube root in real life?
Cube roots come up when you are working with volume. If you know the volume of a cube-shaped container and want to find the length of one side, you use cube root. They also appear in some physics and engineering calculations, and in certain financial formulas.
Is 1/3 the same as 0.333333 when I use the exponent method?
Close enough for most purposes. 1/3 is exactly 0.333... repeating forever, but 0.333333 is close enough that your calculator will give you the right answer. If your calculator lets you type fractions or has parentheses, use (1/3) for slightly more accuracy, but the difference is usually too small to matter.