How to find a cube root
- Enter the number. Negative numbers work, because a negative number has a real cube root.
- Read the cube root and the check that cubing it gives the number back.
- For whole numbers, see the simplified form, such as ∛54 = 3∛2.
Perfect cubes
| n | n³ |
|---|---|
| 1 | 1 |
| 2 | 8 |
| 3 | 27 |
| 4 | 64 |
| 5 | 125 |
| 6 | 216 |
| 7 | 343 |
| 8 | 512 |
| 9 | 729 |
| 10 | 1,000 |
Simplifying cube roots
Look for a perfect cube that divides the number. 54 = 27 × 2, so ∛54 = ∛27 × ∛2 = 3∛2. The calculator does this for whole numbers up to a trillion.
Cube roots without a calculator
Find the perfect cubes on either side. ∛100 is between ∛64 = 4 and ∛125 = 5, a bit closer to 5, and it is about 4.64. Remembering the cubes from 1 to 10 makes these estimates quick.