Perimeter Calculator
Find the perimeter of circles, triangles, rectangles, squares, parallelograms, and trapezoids. Free geometry calculator with instant results, chart, and breakdown view.
About This Calculator
The Perimeter Calculator computes the perimeter (boundary distance) of six common 2D shapes: circle, triangle, rectangle, square, parallelogram, and trapezoid. Simply select the shape you need and enter the required dimensions to get instant results with a visual chart comparison.
Perimeter formulas used by this calculator:
- Circle: C = 2pir (circumference)
- Triangle: P = a + b + c
- Rectangle: P = 2(l + w)
- Square: P = 4s
- Parallelogram: P = 2(a + b)
- Trapezoid: P = a + b + c + d
Regional Notes
This calculator works with any unit of length -- meters, centimeters, millimeters (metric system) or feet, inches, yards (imperial system). The key is to use consistent units for all dimensions. Metric system users typically input in centimeters or meters. Imperial system users input in inches or feet. The perimeter result will be in the same unit as the inputs. Students and professionals worldwide use these same formulas regardless of measurement system -- the math is universal.
This tool is useful for students, teachers, architects, contractors, landscapers, and DIY enthusiasts who need quick perimeter calculations for projects, homework, or construction planning.
Frequently Asked Questions
What is the perimeter of a circle?
The perimeter of a circle is called circumference, calculated as C = 2pir, where r is the radius. It represents the total distance around the circle.
How do you find the perimeter of a triangle?
Perimeter of a triangle is the sum of all three sides: P = a + b + c. For a right triangle, you can also use the Pythagorean theorem to find a missing side before summing.
What is the formula for perimeter of a rectangle?
Perimeter of a rectangle is P = 2(l + w), where l is the length and w is the width. Since opposite sides are equal, you double the sum of length and width.
How do you calculate perimeter of a square?
Perimeter of a square is P = 4s, where s is the side length. Since all four sides are equal, simply multiply one side by 4.
What shapes does this calculator support?
This calculator supports six shapes: circle, triangle, rectangle, square, parallelogram, and trapezoid. Each shape has its own perimeter formula.
Is this calculator free to use?
Yes, all calculators on Calculy are completely free to use with no registration required. Simply enter your dimensions and get instant perimeter results.
Can I share my calculation?
Yes, the URL automatically saves your inputs so you can bookmark or share the exact calculation with others. All results appear in a shareable link.
What units should I use for perimeter measurements?
You can use any consistent unit of length (meters, centimeters, feet, inches, yards). The perimeter result will be in the same unit you entered. For example, entering meters gives meters, entering feet gives feet.