Perimeter CalculatorFind the perimeter of common shapes instantly. Enter dimensions for rectangles, triangles, circles, or regular polygons.
Find the perimeter of common shapes instantly. Enter dimensions for rectangles, triangles, circles, or regular polygons.
Rectangle: P = 2(l + w) | Triangle: P = a + b + c | Circle: C = 2πrTips & Notes
- ✓For irregular shapes, measure each side individually and sum them all.
- ✓The perimeter of a circle is called the circumference.
- ✓Regular polygons have equal sides, so perimeter equals side length times number of sides.
Common Mistakes
- ✗Confusing perimeter with area — perimeter is the distance around a shape, area is the space inside.
- ✗Using diameter instead of radius for circle circumference calculations.
- ✗Forgetting to include all sides when calculating triangle perimeter.
Perimeter Calculator Overview
Perimeter Calculator Overview
The Perimeter Calculator determines the total boundary length of common geometric shapes including rectangles, triangles, circles, and regular polygons. Understanding perimeter is fundamental to countless practical applications — from estimating fencing and trim requirements to calculating the border length for construction projects and craft work.
Perimeter differs from area in that it measures the one-dimensional distance around a shape rather than the two-dimensional space it encloses. This distinction is critical when ordering materials: fencing requires perimeter calculations, while flooring requires area calculations. Mixing these up leads to costly ordering mistakes.
For regular polygons, the calculation simplifies to multiplying one side length by the number of sides. For circles, the perimeter (called circumference) uses the mathematical constant π. For irregular shapes not covered here, measure each distinct side and sum the measurements.