Circle Perimeter Calculator
Our circle perimeter calculator can be of great help if you're struggling to solve geometry problems. One common problem is to find the perimeter of a circle, also called its circumference, which measures the length of the line forming this geometric figure. Keep reading if you want to know:
- What is the formula for circle perimeter.
- How to find the perimeter of a circle using the circle perimeter formula and our circle circumference calculator.
- What are the perimeters of a quarter circle and a half-circle.
🔎 Remember that, as with the rest of our tools, this circle circumference calculator works both ways - it is also a circumference to radius calculator - and you can use it to convert a circumference to a radius.
The circle perimeter formula
If you don't know how to find the circumference of a circle, our calculator is the fastest option. Even so, it's helpful to understand how equations work to interpret the results better. The circle perimeter formula is:
p = 2πr,
p is the circle's perimeter,
r is the radius, and
π is a constant equal to approximately 3.14159265...
You can also express the perimeter in terms of the diameter (
d), remembering that
p = πd
💡 The number π is a constant equal to the ratio of the circumference to the diameter (or twice the radius). It'll always have the same value, independently of the size of the circle.
π in the above equation results in the mentioned ratio:
π = p/(2r).
Half circle and quarter circle perimeter formulas
Sometimes we need to calculate portions of a circle instead of a whole one. We can obtain the formulas for the perimeters of a half-circle and a quarter-circle by dividing the above equation by 2 and 4, respectively:
phalf = πr
pquarter = πr/2
How to calculate the perimeter of a circle?
If you want to use the circle perimeter calculator to find the circumference of a circle, follow these steps:
- Determine the radius of your circle. For example, let's suppose it's 7 cm.
- Input the radius in the calculator, and you'll know the circle's circumference. The result should be 43.982 cm.
- To double-check your result, enter the radius in the circle perimeter formula:
p = 2 × π × (7 cm) = 43.982 cm.
Other helpful tools beyond the circle perimeter calculator
Now that you know how to find the perimeter of a circle don't forget that the circumference to radius calculator is not our only tool dealing with circular objects. We're hopeful that the calculators below will help you with your day-to-day circular problems:
- Circle calc: find c, d, a, r;
- Circle measurements calculator;
- Circle formula calculator;
- Radius of a circle calculator;
- Circle length calculator;
- Circumference to diameter;
- Diameter of a circle calculator;
- Circumference and area of a circle calculator;
- Square footage of a circle calculator; and
- Square inches of a circle calculator.
How do I find the perimeter of a quarter circle?
To find the perimeter of a quarter circle:
- Remember the perimeter of an ordinary circle, which is
p = 2πr.
- Divide it by four, as you only want the perimeter of a quarter circle.
- The result should be
p = πr/2. That is the perimeter of a quarter circle for any radius.
How do I find the perimeter of a half-circle?
Multiply the radius by π (pi), and you'll get the half-circle perimeter. The perimeter of a half-circle is simply the perimeter of an ordinary circle divided by two, which results in
p = πr.
What is the perimeter of a 10-inch circle?
31.416 inches. To find the perimeter of any circle, multiply the diameter by the number pi (π). In this case, 10 in × π = 31.416 in.