About this calculator
Choose what you know and enter it.
How to use it
- Choose what you know.
- Enter it.
- Read the rest.
The formula
Area = s²; perimeter = 4s; diagonal = s√2
- s
- side length
Worked example
Side 8
- Area 64, perimeter 32, diagonal ≈ 11.31.
What the result means
A square plot of 900 sq ft has sides of 30 ft.
Assumptions
- All lengths in the same unit.
Limitations
- Results are rounded to 10 significant figures.
Frequently asked questions
How do I find the side from the area?
Take the square root.
What is the diagonal of a square?
Side × √2.
Is a square a rectangle?
Yes, with equal sides.
Last reviewed on 3 October 2026. Found a mistake? Tell us.