Square Size Calculator
Choose what you know about the square, its side, area, perimeter or diagonal, and enter it with the unit. The calculator gives every other measurement of the square.
- Side
- Area
- Diagonal
Area is entered in square units of the unit you choose.
Every square measurement comes from its side. A square with an area of 25 m² has a side of 5 m, a perimeter of 20 m and a diagonal of 7.07 m. The diagonal is always the side times 1.414.
Square size chart
Side to area. Search for a side.
| Side | Area | Perimeter | Diagonal |
|---|---|---|---|
| 1 | 1 | 4 | 1.414 |
| 2 | 4 | 8 | 2.828 |
| 3 | 9 | 12 | 4.243 |
| 4 | 16 | 16 | 5.657 |
| 5 | 25 | 20 | 7.071 |
| 6 | 36 | 24 | 8.485 |
| 8 | 64 | 32 | 11.314 |
| 10 | 100 | 40 | 14.142 |
| 12 | 144 | 48 | 16.971 |
| 15 | 225 | 60 | 21.213 |
| 20 | 400 | 80 | 28.284 |
| 25 | 625 | 100 | 35.355 |
Same unit.
Area and side
Square metres. Slide the area.
The square and its diagonal are drawn to scale.
How to size a square
Any one to all. Step through it.
Know
One measurement.
Use the diagonal to check a square is truly square on site.
Side, area or diagonal
Starting points. Compare them.
Easiest.
Planning.
Checking.
The 3, 4, 5 rule checks a right angle, the diagonal checks a whole square.
Before you mark out
Square checks. Tick each item.
Tick each item as you go.
Measure both diagonals. If they match, the square is true.
What you get
Square sizing. Each tile explains one result.
Length.
Square units.
Edge.
Corner to corner.
Inside and around.
A square has the shortest perimeter of any rectangle with the same area.
Frequently Asked Questions
No question matches that search.
How do I find the side of a square from its area?
Take the square root of the area.
How do I find the diagonal of a square?
Multiply the side by the square root of two, about one point four one four.
What is the perimeter of a square?
Four times the side.
How big is a square with an area of one hundred square feet?
Ten feet on each side.
How do I check a square is true?
Measure both diagonals. They match on a true square.
What circle fits inside a square?
One with a diameter equal to the side.
Does doubling the side double the area?
No. It makes the area four times bigger.
Every measure of a square
Start from any one measurement and see the whole square, drawn to scale.
More size calculators
Each one has its own calculator, worked examples and answers to common questions.