Square Area Calculator — Area, Perimeter & Diagonal
Enter the side length of a square to instantly get its area (s²), perimeter (4s) and diagonal (s√2) in your chosen unit.
m
Unit
Area = side² (all sides of a square are equal)
- 1
Side length
5 - 2
Area = s²
5 × 5 = 25Area of a square equals the side length squared.
How does this calculator work?
For a square with side s: Area = s², Perimeter = 4s, Diagonal = s√2 ≈ 1.41421 × s. All results are in the same linear unit (or its square for area). A 5 m square has 25 m² area, 20 m perimeter and ≈7.071 m diagonal.
Formula
How this is calculated
A square is a special rectangle where all four sides are equal in length and all four angles are exactly 90°. Because every side equals s, the area is simply side × side = s². Unlike more complex shapes, there is no ambiguity about which dimension to use.
The perimeter — the total length of the boundary — is 4 × s, because there are four equal sides. The diagonal, which runs from one corner to the opposite corner bisecting the square, follows directly from the Pythagorean theorem: d = √(s² + s²) = s√2 ≈ 1.41421 × s.
The formulas hold regardless of the unit you choose. The area will always be in square units of the same type (e.g. if s is in metres, area is in m²). Be careful when converting between area units: 1 m² = 10,000 cm² because both dimensions must be converted, not just one.
Frequently asked questions
A square with side 5 has area = 5² = 25 (in the same square unit as the side — 25 cm² if the side is 5 cm, 25 m² if 5 m, etc.). Its perimeter is 4 × 5 = 20, and its diagonal is 5 × √2 ≈ 7.071.
Rearrange Area = s² to get s = √Area. For example, a square with area 64 m² has a side length of √64 = 8 m. You can enter the known area and work backwards, or use a square-root calculator.
The diagonal connects two opposite corners and equals s × √2, derived from the Pythagorean theorem (the diagonal is the hypotenuse of a right triangle whose legs are both equal to s). For a 1 m square the diagonal is ≈ 1.414 m; for a 10 cm square ≈ 14.14 cm.
Also known as
TG we-Calculate Editorial Team. (2026). Square Area Calculator — Area, Perimeter & Diagonal [Online calculator]. TG we-Calculate. https://we-calculate.com/calculator/square-area-calculator
TG we-Calculate Editorial Team. "Square Area Calculator — Area, Perimeter & Diagonal." TG we-Calculate. 2026. https://we-calculate.com/calculator/square-area-calculator.
TG we-Calculate Editorial Team, "Square Area Calculator — Area, Perimeter & Diagonal," TG we-Calculate, 2026. [Online]. Available: https://we-calculate.com/calculator/square-area-calculator
@misc{wecalculate_square_area_calculator, title = {Square Area Calculator — Area, Perimeter & Diagonal}, author = {{TG we-Calculate Editorial Team}}, howpublished = {\url{https://we-calculate.com/calculator/square-area-calculator}}, year = {2026}, note = {TG we-Calculate} }
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