Calculate the perimeter of 14+ shapes including circles, sectors, ellipses, and polygons. Convert between inches, feet, meters, and more with our precise geometry tool.
How to Calculate Perimeter and Circumference
Perimeter is the total boundary length of a two-dimensional shape. For curved objects, like circles or ellipses, this is known as the circumference. Calculating perimeter correctly is essential for everything from home improvement projects to advanced engineering.
The Circumference Formula
To find the distance around a circle, we use the radius ($r$) and the mathematical constant $\pi$:
Elliptical Perimeter (Ramanujan Approximation)
Because ellipses do not have a simple perimeter formula, we utilize the highly accurate Ramanujan formula:
Perimeter Formula Reference
| Shape | Formula | Key Inputs |
|---|---|---|
| Rectangle | $2(L + W)$ | Length, Width |
| Triangle | $a + b + c$ | Three Sides |
| Sector | $(r \cdot \theta_{rad}) + 2r$ | Radius, Angle |
| Polygon | $n \cdot s$ | Sides, Length |
Frequently Asked Questions
The perimeter of a sector (like a pizza slice) consists of the arc length plus two straight radii:
The perimeter of a circular segment is the sum of the arc length and the chord length:
Yes. Our tool allows you to input measurements in inches, feet, or meters and output the result in your preferred unit automatically using internal conversion factors.