Area of a Square Calculator
This calculator finds the area, perimeter and diagonal of a square from a single side length, using the exact geometric relationships that link a square's four equal sides to everything you need to know about it. Enter the side length and choose a unit, from centimetres, metres, millimetres, kilometres, inches, feet, yards and miles, or type your own custom label such as tiles or blocks. The calculator instantly returns three results: the area (side squared), the perimeter (four times the side) and the diagonal (side multiplied by the square root of two), each shown in a live worked example, a full breakdown of every step, and a plain-English summary sentence. It also lists the formulas used, plus the reverse formulas for working back to the side length from a known area, perimeter or diagonal. Because a square has four equal sides and four right angles, only one measurement is ever needed, and every result updates instantly as you change the side length or unit. Use it for maths homework, tiling and paving quantities, fencing runs, land measurements or any job where you need to move quickly between area, perimeter and diagonal. Results are mathematically exact for the number you enter, so the only uncertainty comes from how precisely you measured the side length in the first place.
1. Square Dimensions
2. Worked Example
For a square with side length 5 m:
The worked example updates with your inputs.