Square Calculator for Side Length, Diagonal, Perimeter and Area

Updated October 13, 2026By Unit Conversion Plus

Enter the side, diagonal, perimeter or area to solve every main measurement of a square.

Known measurement

P = 4s · A = s² · d = s√2

Because every side is equal and each corner is a right angle, one known measurement is enough to solve the square.

Use s = √A when area is known, or s = P ÷ 4 when perimeter is known.

Side, diagonal and perimeter use length units. Area is reported in the corresponding square unit.

How do I find a square's diagonal?

Multiply its side length by √2.

Can two squares have the same perimeter but different areas?

No. A square's perimeter uniquely determines its side and therefore its area.