Perimeter Calculator — Rectangle, Triangle, Circle & More
Quick answer: Select a shape and enter dimensions to find perimeter and area.
Calculate the perimeter of any 2D shape: rectangle, square, triangle, circle (circumference), and regular polygons. Also shows the area of each shape. Select your shape and enter dimensions.
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Last reviewed: April 2026Report an error
Perimeter
26
Perimeter = 26. Area = 40.
Perimeter
26
Area
40
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How to Use This Perimeter Calculator Calculator
- 1Select the shape.
- 2Enter the required dimensions.
- 3Read the perimeter and area.
Frequently Asked Questions
- P = 2(l + w), where l = length and w = width. It is the total distance around the rectangle.
- The perimeter of a circle is called the circumference: C = 2πr = πd.
- P = a + b + c (sum of all three sides). For a right triangle with legs 3 and 4: hypotenuse = 5, P = 12.
- A polygon where all sides are equal length and all interior angles are equal. Examples: equilateral triangle (3 sides), square (4), pentagon (5), hexagon (6).
- Perimeter is the distance around the outside (1D, in linear units). Area is the space inside (2D, in square units).
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