Square Root √

The Square Root character (√) is a standard HTML entity defined in the HTML specification. In HTML source code, it can be written using the named entity reference √, the decimal numeric character reference √, or the hexadecimal numeric reference √. The character is assigned Unicode code point U+221A in the Universal Character Set.

The square root symbol indicates the principal square root of the expression under it. It is one of the most fundamental mathematical operations and appears in geometry (Pythagorean theorem), statistics (standard deviation), physics, and engineering. The radical sign has been used in mathematical notation since the 16th century.

Mathematical HTML entities enable web authors to display proper mathematical notation without relying on images or specialized rendering libraries like MathJax or KaTeX. While complex equations and multi-line formulas may still benefit from dedicated math typesetting tools, individual symbols expressed as HTML entities render quickly, remain accessible to screen readers, and can be styled with CSS just like regular text content.

When deciding how to encode the Square Root character in your HTML documents, the named entity √ is generally the most readable choice for developers reviewing or maintaining source code. The decimal form √ and hexadecimal form √ are equally valid alternatives that work in contexts where named entities may not be supported, or when generating HTML output programmatically from server-side code. All three representations produce identical visual output in every modern web browser.

Use the square root symbol for mathematical expressions involving roots, such as the Pythagorean theorem (c = √(a² + b²)) and standard deviation formulas. For proper rendering of the vinculum (horizontal bar extending over the radicand), a math rendering library is recommended for complex expressions.