Key takeaways
- The perimeter of a square is P = 4s, four times the side.
- Only one measurement is needed, since all four sides are equal.
- Perimeter uses regular units, such as cm or inches, not squared units.
- For a fixed amount of edging, a square shape gives more area than a narrow rectangle.
In this guide
What is the perimeter of a square?
A square has four sides that are all the same length. The perimeter is the total distance around the outside, measured in regular units such as cm or inches.
Why does the perimeter of a square matter?
Perimeter tells you exactly how much edging, trim, or fencing a square shape needs — and a square is often the most space-efficient choice for a given amount of material.
With 28 m of edging, a 7 m × 7 m square bed covers 49 m². The same 28 m of edging reshaped into a 10 m × 4 m rectangle only covers 40 m² — 9 m² less growing space, for the exact same material.
The formula
| Symbol | What it means | Example |
|---|---|---|
| P | The perimeter, total distance around | 28 m |
| s | The side length: any one side | 7 m |
Since all four sides are equal, the perimeter is simply the side length multiplied by 4.
How to find the perimeter step by step
- 1Measure one side. Since all four sides are equal, one measurement is enough.
- 2Multiply the side length by 4.
- 3Add regular units. Such as cm or inches, not squared.
Try it below: change the side length and watch the perimeter update, with every step shown.
Try it yourself
Pre-filled with the example — change any value.
Common mistakes to avoid
- Measuring the diagonal by accident. The diagonal cuts across the square and is longer than a side; it isn't used in this formula.
- Using square units. Perimeter is a length, so the answer should be in units like cm, not cm².
- Forgetting all four sides are equal. You never need to measure more than one side.
Tips and tricks
- For a shape where sides differ, use the more general perimeter of a rectangle calculator instead.
- Once you have the side, you can immediately find the area of the square by squaring it.
Where you'll use it in real life
- Home decor: framing a square photo or mirror.
- Crafts: measuring trim for a square rug or quilt.
- Gardening: working out fencing for a square garden plot.
- Construction: checking material for a square window or panel border.
Quick summary
To find the perimeter of a square, multiply the side length by 4. Only one measurement is needed, and the answer is always in regular units, not squared. Use the calculator above to check your own square in seconds.
Worked example
You're installing edging around a square flower bed with sides of 7 meters. How much edging material do you need to go all the way around?
- 01P = 4s
- 02P = 4 × 7
- 03P = 28 m
These numbers are pre-filled in the calculator above.
Frequently asked questions
How do I find the perimeter of a square from its area?
Take the square root of the area to get the side length, then multiply that side length by 4.
What's the difference between perimeter and area of a square?
Perimeter (4s) is the distance around the edge, in regular units. Area (s²) is the space inside, in square units. Use the [area of a square calculator](/calculator/area-square) for the space inside.
Is the perimeter of a square always a multiple of 4?
Only if the side length itself is a whole number. In general the perimeter is simply 4 times whatever the side length is, whole number or not.
How is the perimeter of a square different from a rectangle's?
A square's perimeter formula (4s) is a shortcut version of a rectangle's [2(l + w)](/calculator/perimeter-rectangle) formula, used because all four sides of a square are equal.
