What is the formula for the perimeter of a square?

Perimeter = 4 × s, where s is the length of one side. For example, a square with a side of 7 meters has a perimeter of 4 × 7 = 28 meters.

How do I find the side length from the perimeter?

Divide the perimeter by 4: s = P ÷ 4. For example, if the perimeter is 36 cm, the side length is 36 ÷ 4 = 9 cm.

Why is the perimeter 4 times the side?

A square has four equal sides, so the total distance around it is simply four times one side length.

What units does this calculator use?

The calculator is unit-agnostic. Enter your side length in any unit (meters, feet, inches, etc.) and the perimeter is returned in the same unit.

How is perimeter different from area?

Perimeter is the total distance around the outside of the square (P = 4s), measured in linear units. Area is the space enclosed inside (A = s²), measured in square units.

Can I use this for a rectangle?

No — a rectangle has two different side lengths. Use a rectangle perimeter calculator (P = 2l + 2w) for non-square rectangles. This tool is optimized for squares only.

Perimeter of a Square Calculator

Enter a side length to get the perimeter of a square instantly, or reverse-calculate the side from a known perimeter.

Calculate From

Side Length (s)

units

Formulas

Perimeter P = 4s

Side from Perimeter s = P ÷ 4

Enter a value on the left to calculate

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Summary

This calculator computes the perimeter of a square using the formula P = 4s, where s is the side length. Enter any side length and get the perimeter instantly. You can also work in reverse — enter a known perimeter to calculate the corresponding side length. All computation happens in your browser with no data sent to a server.

How it works

Choose whether to start from the side length or a known perimeter.
Enter your value in the input field.
The calculator applies P = 4s (or s = P ÷ 4) instantly.
Read the result along with the step-by-step formula breakdown.
Click "Copy Result" to copy the output to your clipboard.

Use cases

Find the total fencing needed to enclose a square yard or garden.
Calculate how much trim or molding is required for a square room.
Verify geometry homework answers for square perimeter problems.
Convert a known perimeter back into a side length for construction planning.
Estimate the border length of square tiles, panels, or frames.
Use in drafting, landscaping, or interior design calculations.

Frequently Asked Questions

Last updated: 2026-05-28 · Reviewed by Nham Vu