Calculate perimeter for squares, rectangles, triangles, circles, parallelograms, and trapezoids.
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Shape
Geometry
The perimeter calculator finds the perimeter (total boundary length) of squares, rectangles, triangles, circles, parallelograms, and trapezoids from their dimensions.
Square: 4 times side. Rectangle: 2(length + width). Triangle: sum of three sides. Circle (circumference): 2 pi r. Parallelogram: 2(base + side). Trapezoid: sum of all four sides.
For circles, the perimeter is called the circumference. All other shapes use the sum of their side lengths.
This calculator covers regular shapes. For irregular polygons, sum the individual side lengths manually. The extra explanation keeps the page useful for searchers who need to understand not just the number, but also the assumption set behind it.
A worked example helps translate the perimeter of common 2d shapes maths into a realistic scenario so the user can compare the headline result with a concrete set of inputs.
That matters because a result is easier to trust when the page shows how the same logic behaves in a practical case instead of leaving the formula abstract.
Frequently asked questions
Perimeter is the total length around the boundary of a shape (measured in linear units). Area is the space enclosed within the boundary (measured in square units).
The circumference is 2 times pi times the radius, or pi times the diameter.
The safest manual check is to follow the same formula or rule one step at a time and compare that working with the calculator output. That catches sign errors, bracket mistakes, and input-order mixups without requiring any extra method beyond the underlying maths itself.
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