Area of Square Calculator
Calculate a square's area, perimeter and diagonal from its side length — area = side², perimeter = 4 × side, diagonal = side × √2. Pick any unit; it's carried through as a label, no conversion needed.
Input
Output
| Metric | Value |
|---|---|
| No data yet | |
Guides
A square is the simplest shape to measure: every side is the same length, so one number — the side length — is enough to derive everything else about it. This calculator takes that single measurement and returns the area, perimeter and diagonal at once.
The formulas
For a square with side length s:
Area = s²
Perimeter = 4 × s
Diagonal = s × √2
Area comes from multiplying the side by itself, since a square's width and height are identical. Perimeter is just the four equal sides added together. The diagonal follows from the Pythagorean theorem: it's the hypotenuse of a right triangle formed by two sides, so it works out to the side length times the square root of 2 (≈ 1.41421356).
Worked example: a square with a 5 cm side has an area of 25 cm², a perimeter of 20 cm, and a diagonal of roughly 7.07 cm.
How to use it
- Enter the side length of your square.
- Pick a unit (millimeters, centimeters, meters, kilometers, inches, feet, or yards) — this is purely a label on the results, since area, perimeter and diagonal are all calculated in whatever unit you entered the side in. No unit conversion is applied.
- Area, perimeter and diagonal update instantly as you type.
FAQ
Does the unit dropdown convert my measurement? No. It labels the output (e.g. "cm" vs "in") but performs no conversion — the side length you enter and the results you get are in the same unit. If you need to convert between units first, use a length converter, then paste the result here.
Why does area use a squared unit (cm²) but perimeter and diagonal don't? Area measures a two-dimensional surface, so its unit is squared (length × length). Perimeter and diagonal are both one-dimensional distances, so they stay in the plain unit you entered.
What if I enter a negative or blank side length? The calculator requires a non-negative side length before it will compute a result; a blank or invalid entry simply produces no output rather than an error.
Can I use this for a rectangle instead? No — this tool assumes all four sides are equal. For a rectangle (different length and width), you'd need separate length × width and 2 × (length + width) formulas.
How precise are the results? Values are rounded to two decimal places, which is precise enough for most everyday and classroom use. The underlying calculation itself is exact; only the displayed figure is rounded.
Privacy
Everything runs locally in your browser — the side length you enter is never uploaded or stored anywhere.