Whether you're drawing a blueprint, doing a hand job, calculating how much fence to use to protect your garden jacuzzi, or just solving a math problem, knowing how to find the circumference of a circle will help you find the solution to your problems. Read on to find out how to calculate the circumference of a circle.
Steps
Method 1 of 2: Calculate the Circumference Using the Diameter
Step 1. Write the formula for calculating the circumference of a circle:
C = π * d. C represents the 'circumference', i.e. the value you are looking for, and 'd' is the length of the diameter of the circle in question. You have all the data to calculate the circumference. Using a calculator, multiply the diameter value by π. The value of pi is a number with infinite decimal places, but by convention the rounded value of 3, 14 is used.
Step 2. Substitute the known value of the diameter for 'd' and solve the equation
For example, let's assume that you have a 2.5m diameter pool and you want to enclose it so that you have a usable space around the pool of 2m. To calculate the length of the fence to use, first, you will need to find out what the diameter of the circle in question is. In our case the diameter will be given by the sum of the diameter of the tank and the free space around it, i.e. 2.5 m + 2 m + 2 m. The final diameter of the circle to be fenced will therefore be 6.5 m. Now you can use this value in the formula and solve your problem:
- C = π * d
- C = π * 6, 5
- C = 20.41 m
Method 2 of 2: Calculate the Circumference Using the Radius
Step 1. Write the formula for calculating the circumference of a circle using the radius
The radius of a circle is equal to half the diameter, so you can also indicate the diameter with the words '2r'. Substituting this information with the previous formula you will get what you need in this case, that is C = 2πr. In this formula 'r' represents the radius of the circle while the value of pi is a number with infinite decimal places, by convention rounded to 3, 14.
Step 2. Substitute the known value of the radius for 'r' and solve the equation
For example, imagine you need to cut out a strip of paper to wrap around the edge of a freshly made cake. Imagine that the radius of the cake is 5 cm. To calculate the circumference of the pie you will simply have to enter the radius value in the known formula:
- C = 2π * r
- C = 2π x 5
- C = 10π
- C = 31.4 cm
Advice
- Consider purchasing a more advanced calculator than the regular ones, so that it already has the π value stored in one of the buttons. Using this type of calculator will require less effort on your part to type the numbers, and will also provide a more accurate answer since the π button will use an approximate number with many more digits after the decimal point in the calculation than 3, 14.
- Check with your teacher or do some research.
Warnings
- Remember to always double check your calculations as a single mistake can change all your data.
- Take your time. With practice the calculations will become immediate.
- If you are stuck, ask a friend, relative or teacher for help; they will definitely help you!
