Calculate rectangle area.
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Perimeter of a Rectangle Calculator
Quick answer
If length is 12 and width is 8, the perimeter is 40 units.
Rectangle perimeter: Perimeter = 2 × (length + width).
Enter your values
Perimeter
40units
The total distance all the way around the outside edge.
You enter Length 12, Width 8. You get Perimeter 40 units.
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About the Perimeter of a Rectangle Calculator
The perimeter of a rectangle is the total distance around its edges. It tells you how much fencing, skirting or border you need. Enter the length and the width.
A rectangle 12 m by 8 m has a perimeter of 40 m.
Rectangle perimeter
Perimeter = 2 × (length + width)
Things to keep in mind
- Use the same unit for both sides; the answer is in that unit.
- Add some extra length for corners, gates or wastage when buying material.
- The perimeter is different from the area, which measures the space inside.
See how the result changes
Each table re-runs this calculator with one value changed and everything else left as it is.
Perimeter by length
If length goes from 12 to 18, perimeter changes from 40 units to 52 units (+30%).
| Length | Perimeter |
|---|---|
| 6 | 28 units |
| 9 | 34 units |
| 12start | 40 units |
| 18 | 52 units |
| 24 | 64 units |
Perimeter by width
If width goes from 8 to 12, perimeter changes from 40 units to 48 units (+20%).
| Width | Perimeter |
|---|---|
| 4 | 32 units |
| 6 | 36 units |
| 8start | 40 units |
| 12 | 48 units |
| 16 | 56 units |
MATH GUIDE
A quick guide to Rectangle Perimeter
Use it to get an accurate perimeter in seconds — free, with no sign-up.
Instant results
See your perimeter the moment you enter your numbers.
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Every calculator here is free to use, with no account required.
Accurate & transparent
The same standard formula runs on our server for every calculation.
How to Use the Rectangle Perimeter Calculator
1
Enter Length
Provide your length.
2
Enter Width
Provide your width.
3
View Your Results
Get your perimeter instantly, calculated on our server.
What is Rectangle Perimeter?
This math tool works out your perimeter instantly, so you don't have to do the math by hand.
“One quick calculation, so you always know your perimeter before you decide.”
What Affects Your Perimeter
Your perimeter depends on the values below.
Length
Changing your length changes your perimeter.
Width
Changing your width changes your perimeter.
Example Result
Here's what you can expect from a rectangle perimeter calculation:
- Length
- 12
- Width
- 8
- Perimeter
- 40 units
Frequently Asked Questions
- How does length affect perimeter?
- If length goes from 12 to 18, perimeter changes from 40 units to 52 units (+30%).
- How does width affect perimeter?
- If width goes from 8 to 12, perimeter changes from 40 units to 48 units (+20%).
- How to calculate rectangle perimeter?
- Fill in length and width in the Perimeter of a Rectangle Calculator above and your perimeter is calculated instantly. Change any value to see how the result responds.
- What does an example rectangle perimeter calculation look like?
- If length is 12 and width is 8, the perimeter is 40 units.
- Is this calculator free to use?
- Yes — every calculator on this site is completely free, with no sign-up or account required.
- How accurate is this calculator?
- It uses the standard formula and calculates on our server for every request, so results are precise for the values you enter.
- Is my data saved anywhere?
- No. Nothing you enter is stored or sent anywhere unless you choose to share a link with your values included.
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