What is the Perimeter Calculator?
Add up any number of side lengths to get the perimeter of a polygon. Perimeter is the total distance around a shape, the measurement you need for fencing, trim, edging and borders.
How to use the Perimeter Calculator
- Enter your side lengths.
- Results update automatically as you type; you can also press Calculate.
- Read the output: perimeter, number of sides.
- Use the 📊 chart to see the result visually, then copy or share it.
Formula and method
Worked example
With side lengths = 5, 7, 5, 7, the Perimeter Calculator returns perimeter: 24; number of sides: 4.
Where the Perimeter Calculator helps in real life
You are putting baseboard trim around an L-shaped room. Entering each wall length gives the total, so you can buy enough lengths in one trip.
A farmer fences an irregular five-sided paddock. Adding the five measured sides gives the length of fencing wire to order.
Common mistakes to avoid
- Leaving out a short side on irregular shapes.
- Mixing feet and inches between sides.
- Including door openings that will not get trim.
- Measuring curved edges as straight lines.
💡 Practical tip: Add a little extra material for cuts and joins — trim and fencing rarely come in exactly the lengths you need.
Tips for better results
- Sketch the shape and number each side before measuring.
- Subtract doorways when buying trim.
- Add 10% for cuts and joins.
Frequently asked questions
What does the Perimeter Calculator do?
Add up any number of side lengths to get the perimeter of a polygon.
How is it calculated?
The Perimeter Calculator uses this method: P = sum of all sides.
Can you show an example?
With side lengths = 5, 7, 5, 7, the Perimeter Calculator returns perimeter: 24; number of sides: 4.
Is the Perimeter Calculator accurate?
Yes. It uses standard formulas and exact constants, and the results are verified by our automated test suite. Values are displayed to up to 12 significant digits.
Is this tool free and private?
Yes — the Perimeter Calculator is completely free with no sign-up, and it runs entirely in your browser, so the values you enter are never uploaded to our servers.
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