Whether you're fencing a yard, framing a picture, or working through a geometry assignment, this collection has the right tool. The Rectangle Perimeter Calculator, Circle Perimeter Calculator, and Square Perimeter Calculator handle the classics, while the Octagon Perimeter Calculator and Isosceles Triangle Perimeter Calculator cover the less-standard shapes.
Browse the most-popular list or open the Trending tab to see what other visitors are measuring. Every calculator is free, needs no account, and works on any device.
- Volume Calculator
- Area Calculator
- Perimeter Calculator
- Surface Area Calculator
- Circle Calculator
- Rectangle Calculator
- Triangle Calculator
-
Arc Length from Degrees CalculatorCalculate the arc length of a circle from its radius and central angle in degrees. Also shows radians and full circumference instantly.
-
Perimeter of a Circle CalculatorCalculate the perimeter (circumference) of a circle from its radius using P = 2πr. Also shows diameter and area. Fast, free and accurate.
-
Circle Perimeter from Diameter CalculatorCalculate the perimeter (circumference) of a circle from its diameter using C = πd. Instantly get circumference, radius, and area for any diameter.
-
Semicircle Perimeter CalculatorCalculate the perimeter of a semicircle from its radius using P = πr + 2r = r(π + 2). Free, instant, and shows the arc and diameter parts.
-
Equilateral Triangle Perimeter CalculatorCalculate the perimeter of an equilateral triangle instantly using P = 3a. Enter the side length to get the total perimeter in one click.
-
Perimeter of a Rectangle CalculatorCalculate the perimeter of a rectangle instantly using P = 2(l + w). Enter length and width to get perimeter, area, and diagonal.
-
Circle Circumference from Area CalculatorFind the circumference of a circle from its area instantly. Enter the area and get the circumference, radius, and diameter using C = 2√(πA).
-
Diameter from Circumference CalculatorFind the diameter of a circle from its circumference using d = C / π. Instantly calculate diameter and radius from any circumference value.
-
Radius from Circumference CalculatorFind the radius of a circle from its circumference using r = C / (2π). Also returns diameter and area instantly in the same unit.
-
Perimeter of a Square from Area CalculatorFind the perimeter of a square from its area instantly. Enter the area and get the side length and perimeter using P = 4√A. Free, fast, accurate.
-
Room Perimeter Calculator for Baseboard & TrimCalculate the perimeter of a rectangular room and the linear feet of baseboard or trim you need, minus doorways and plus a waste allowance.
-
Perimeter of an L-Shape CalculatorCalculate the perimeter of an L-shaped figure from its overall outer width and height using P = 2 × (a + b). Fast, free, and accurate.
-
Circumference of a Circle CalculatorCalculate the circumference of a circle from radius or diameter using C = 2πr = πd. Get circumference, diameter, and area instantly with worked examples.
-
Circumference from Radius CalculatorCalculate the circumference of a circle from its radius using C = 2πr. Instantly get circumference, diameter, and area from any radius value.
-
Missing Side of a Rectangle from Perimeter CalculatorFind the unknown side of a rectangle from its perimeter and one known side. Uses missing_side = P/2 − known_side. Instant, free, and accurate.
-
Right Triangle Perimeter from Two Legs CalculatorFind the perimeter of a right triangle from its two legs. Enter leg a and leg b to get the hypotenuse and total perimeter instantly.
-
Pentagon Perimeter CalculatorCalculate the perimeter of a regular pentagon instantly using P = 5s. Enter one side length and get the total perimeter in any unit.
-
Rhombus Perimeter CalculatorCalculate the perimeter of a rhombus instantly with P = 4a. Enter the side length and get the total perimeter in any unit. Free and accurate.
-
Square Side from Perimeter CalculatorFind the side length of a square from its perimeter using s = P/4. Also returns the square's area and diagonal instantly.
-
Hexagon Perimeter CalculatorCalculate the perimeter of a regular hexagon instantly using P = 6s. Enter one side length and get the total perimeter with the formula explained.
-
Arc Length from Radius and Radians CalculatorCalculate arc length from a circle's radius and central angle in radians using s = r × θ. Free, instant, with chord length too.
-
Triangle Perimeter & Semiperimeter CalculatorCalculate the perimeter and semiperimeter of a triangle from its three sides, with a Heron's formula area check and triangle inequality validation.
-
Square Perimeter from Area CalculatorFind the perimeter of a square from its area using P = 4√A. Enter the area to instantly get the side length and perimeter. Free and accurate.
-
Perimeter of a Pentagon CalculatorCalculate the perimeter of a regular pentagon instantly with P = 5s. Enter one side length and get the total distance around all five sides.
Frequently asked questions
Which shapes can I calculate the perimeter of here?
The collection covers circles (circumference), rectangles, squares, parallelograms, kites, isosceles triangles, octagons, and right triangles, among other shapes. Whether for a fencing estimate, a homework problem, or a design task, there is a dedicated calculator ready to use.
How accurate are the perimeter results?
Each calculator applies the standard geometric formula for its shape, verified against known reference values. Results are dependable for everyday tasks, but for construction, structural work, or safety-critical applications, confirm your figures against the governing standard and have a qualified engineer review them.
Are these perimeter calculators free?
Yes — every tool in this collection is completely free, with no account required and no subscription. Open any calculator, enter your dimensions, and get the perimeter instantly. No registration of any kind is needed.
Does the site store the measurements I enter?
Nothing you type is stored or sent to our servers. All calculations run entirely within your browser, and your data never leaves your device. Close the page and your entries are gone.
How can I find the most-used perimeter calculators quickly?
The page list is sorted by real visitor usage, with the most popular tools first. The Trending tab shows what is seeing the most activity right now, and Recently Added highlights the newest tools in the collection.
