What a cube root is
The cube root of a number is the value that, multiplied by itself three times, gives that number. ∛27 = 3 because 3 × 3 × 3 = 27, and ∛64 = 4. It is the reverse of cubing, which is written with a superscript three: 4³ = 64 (see the cubed symbol page).
Unlike square roots, cube roots of negative numbers are ordinary real numbers: ∛−8 = −2, because (−2) × (−2) × (−2) = −8. Cube roots also show up in geometry: a cube with a volume of V has sides of length ∛V.
How to type the cube root symbol
∛ has its own Unicode character, U+221B, but no Alt code or Mac Option shortcut, so the quickest way is to copy it here. In Microsoft Word, type 221B and press Alt + X. On a Mac, open the Character Viewer (Control + Command + Space) and search for "cube root".
In LaTeX, write \sqrt[3]{x}; the same command with a 4 gives a fourth root. In HTML there is no named entity, so use the numeric code ∛. If a font does not show ∛, the fallback ³√ (a superscript three followed by √) is understood everywhere.
Fourth roots, nth roots and Excel
Unicode stops at ∜, the fourth root. For a fifth or higher root, put a superscript number before the square root symbol, like ⁵√32 = 2. You can find more raised digits on the superscript symbols page.
Excel has no dedicated cube root function, so raise the number to the power of one third: =27^(1/3) or =POWER(27, 1/3) both return 3, and the same formulas work in Google Sheets. The parentheses around 1/3 matter, because =27^1/3 calculates 27 divided by 3.