Geometry & Shapes
Perimeter Calculator
Perimeter — it sums the side lengths (or applies the shape's perimeter formula) for the figure you choose. This page runs that same calculation on your numbers, in your browser: no signup, no uploads, nothing stored.
Give Perimeter Calculator your shape, length, width and side and it returns the perimeter straight away. Built to find the perimeter of a shape, it runs entirely on your device.
About this calculator
It sums the side lengths (or applies the shape's perimeter formula) for the figure you choose. That is the whole of the calculation — the mistakes happen in the inputs. It matters whenever a shape has to be measured, cut, covered or compared and the geometry has to be right first. Worked example: Perimeter of a rectangle 8 m × 5 m = 2 × (8 + 5) = 26 m . Use the calculator with your own figures; it runs entirely on your device.
How to use
- Choose the shape you want the perimeter of.
- Fill in the dimensions for that shape only.
- Press Calculate to find the perimeter.
- Read the perimeter (or circumference for a circle).
Why use Perimeter Calculator
Fast
Calculations run in your browser. No round trip to a server.
Private
Your inputs never leave your device. Nothing is uploaded.
Free
No signup, no paywall, no ads-in-results, no watermarks.
Accurate
Uses standard formulas where applicable; check critical results before relying on them.
Mobile-ready
Optimised for phones, tablets, and desktops alike.
Transparent
Honest disclaimers wherever browser limits or regional rules apply.
Common uses
Use it when comparing two shapes
Use it for flooring and tiling estimates
Use it when drafting plans and sketches
Use it for fencing and edging lengths
Use it when teaching shape area
Use it for quick area and perimeter checks
Technical notes
Perimeter Calculator sums the side lengths (or applies the shape's perimeter formula) for the figure you choose.
Results assume exact, idealised shapes; real-world measurement error is not included.
Because it runs locally, results appear instantly with no server round-trip.
FAQ
Which shapes can this calculate the perimeter of?
It covers rectangles, squares, circles, triangles, and regular polygons; choose the shape, then enter its dimensions.
Why does a circle show circumference instead of perimeter?
Circumference is simply the name for the distance around a circle, so that label is used for circles.
Do I need to fill in every field?
No. Only fill in the fields for the shape you selected; the others are ignored.
Does the Perimeter Calculator send my data to a server?
No. The Perimeter Calculator runs entirely in your browser, so nothing you enter is uploaded, stored, or shared.
Worked example
Perimeter of a rectangle 8 m × 5 m = 2 × (8 + 5) = 26 m.