How to type Alt+251
- Make sure Num Lock is on.
- Hold down the Alt key.
- Type 251 on the numeric keypad. The number row above the letters will not work.
- Release Alt. The square root symbol √ appears.
Alt+251 is a classic code from the CP437 table used by the original IBM PC, which is why there is no leading zero. This symbol does not exist on the Windows-1252 table, so the classic code is the only Alt code for it.
On a laptop without a numpad
Press Win+. to open the emoji panel, pick the Symbols tab and search for "square root". Or open Character Map from the Start menu. In Microsoft Word you can type 221A followed by Alt+X. Some laptops have a hidden numpad on the J, K, L, U, I and O keys that activates with Fn.
On a Mac
Alt codes do not exist on macOS, but this symbol has a shortcut: press Option+V.
In HTML and code
Use √ in HTML, "\221A" in CSS and "\u221A" in JavaScript. See the Square Root Symbol guide for every platform.
Frequently asked questions
What does Alt+251 type?+
Alt+251 types the square root symbol, √ (Unicode U+221A). Hold Alt, type 251 on the numeric keypad, then release Alt.
Why do I need the code without a zero?+
Alt+251 is a classic CP437 code from the original IBM PC character set. It has no leading zero.
Alt+251 does not work. Why?+
Check that Num Lock is on and that you are using the numeric keypad rather than the number row. Laptops without a numpad cannot enter Alt codes: use Win + . for the symbol panel, Character Map, or copy the symbol from this page.
How do I type √ on a Mac?+
Press Option+V on a Mac. Alt codes themselves do not work on macOS.