Area of a circle
How to Calculate the Area. The area of a circle is: ? (Pi) times the Radius squared: A = ? r2. or, when you know the Diameter: A = (? /4) ? D2. or, when you know the Circumference: A = C2 / 4?. Jul 28, · You can easily calculate everything, the area of a circle, its diameter, and its radius, using our area of a circle calculator in a blink of an eye: Determine whether your given value is a diameter or a radius using the picture on the right and definitions available in Enter your value into the.
This article was co-authored by Grace Imson, MA. Grace Imson is a math teacher with over 40 years of teaching experience. She has taught math at the elementary, middle, high school, and college levels. This article has been viewed 89, times. Log in Social login does not work in incognito and private browsers.
Related Articles. Part 1 of All rights reserved. This image may not be used by other entities without the express written consent of wikiHow, Inc. Set up the formula for finding the circumference of a circle. Plug the circumference into the formula. For example, if you know the circumference of a circle is 25 centimeter 9. Divide both sides of the equation by 2. Divide both sides of the equation by 3. For example: Part 2 of Set up the formula for finding the area of a circle.
Plug the radius into the formula. Then, square the value. To square a value means to multiply it by itself. For example, if you what cells make up the esophagus the radius to be 3. If you are not using a calculator, you can use the rounded how to measure force of a punch 3.
The product will give you the area of the circle, in square units. Part 3 of Set up the formula for the circumference of a circle, as a function of its area. This information should be given to you. For example, if you know the circumference is 25 centimeter 9. Remember that what you do to one side of an equation, you must do to the other side as well.
Square both sides of the equation. When you square a value, you multiply the value by itself. Squaring a square root cancels the square root, leaving you with the value under the radical sign. Remember to keep the equation balanced by squaring both sides. Divide each side of the equation by 3. This is the area of the circle, in square units.
Divide the circumference by 3. Divide by 2: that gives you the radius. Square the radius, and multiply that by pi: that gives you the area. Yes No. Not Helpful 10 Helpful Not Helpful 16 Helpful 9. Include how to solve area of circle email address to get a message when this question is answered. Related wikiHows How to.
How to calculate the area of a circle? Area of a circle formula
Area of a circle formula. The formula for the area of a circle is ? x radius2, but the diameter of the circle is d = 2 x r 2, so another way to write it is ? x (diameter / 2)2. Visual on the figure below. The area of a circle is the region enclosed by the circle. The area of a circle is equals to pi (?) multiplied by its radius squared. Pi (?) is the ratio of the circumference of a circle to its diameter. Pi is always the same number for any circle. Jul 07, · We can also calculate the area directly using diameter. Formula of area of circle in the form of diameter is. Area = pi * (diameter/2)*(diameter/2) Area = (1/4)* pi * d 2. For the sake of understanding, we will solve the previous example using the formula of a diameter. As the radius is given as cm. we can convert it into the diameter.
Last Updated: April 8, References. This article was co-authored by Grace Imson, MA. Grace Imson is a math teacher with over 40 years of teaching experience. She has taught math at the elementary, middle, high school, and college levels.
There are 16 references cited in this article, which can be found at the bottom of the page. This article has been viewed 5,, times. A common problem in geometry class is to have you calculate the area of a circle based on provided information. The formula is simple and only needs the radius of the circle to find its area. However, you also need to practice converting some other bits of provided data into terms that can help you use this formula.
The most common error when using diameter is forgetting to square the denominator. If you don't divide the diameter by 2 to find the radius, you can still find the area of the circle. However, you need to change the formula so that you square the 'd' otherwise your answer will be wrong.
You can find the area of a circle using the radius, the diameter, or the circumference. For example, if the radius of the circle is 6 inches, first you would square 6 and get Therefore, the area of the circle is To find the area using the diameter, or the distance from one side of the circle to the other, first divide the diameter in half to find the radius.
For example, if the diameter is 20 inches, you would divide that in half and get 10 inches. For example, if the circumference is 42 inches, first you would square 42 and get 1, Finally, you would divide 1, by If you want to find the area of a sector from a circle, keep reading the article!
Method 1 of Identify the radius of a circle. The radius is the length from the center of a circle to the edge of the circle. You can measure this in any direction and the radius will be the same. The radius is also one half of the diameter of a circle. The diameter is the line segment that passes through the center and connects opposite sides of the circle.
It can be difficult to measure to the exact center of a circle, unless the center is already marked for you on a circle drawn on paper. For this example, assume that you are told that the radius of a given circle is 6 cm. Square the radius. This variable is squared. Multiply by pi. The true decimal value continues on infinitely. Report your result. If the radius was measured in centimeters, the area will be in square centimeters. If the radius was measured in feet, the area will be in square feet.
If you do not know, then report both. Method 2 of Measure or record the diameter. Some problems or situations will not provide you with the radius. Instead, you may be given the diameter of a circle.
If the diameter is drawn into your diagram, you can measure it with a ruler. Alternatively, you may just be told the value of the diameter. Assume for this example that the diameter of your circle is 20 inches. Divide the diameter in half.
Remember that the diameter is equal to double the radius. Therefore, whatever value you are given for the diameter, cut it in half and you will have the radius. Use the original formula for area. Report the value of the area. Recall that your area is to be reported in square units. In this example, the diameter was measured in inches, so the radius is in inches.
Therefore, the area will be reported in square inches. You can also provide the numerical approximation by multiplying by 3. This will give a result of 3. Method 3 of Learn the revised formula. If you know the circumference of a circle, you can use a revision of the formula for the area of a circle.
This revised formula uses circumference directly, without the radius, to find area. Measure or record the circumference. In some real world situations, you may not be able to measure the diameter or radius accurately. If the diameter is not drawn for you or the center is not identified, it can be difficult to approximate the center of a circle. For some physical circles - a pizza pan or a frying pan, for example - you may be able to use a tape measure and measure the circumference more accurately than you can measure the diameter.
Use the relationship between circumference and radius to revise the formula. The circumference of a circle is equal to pi times the diameter. Substitute into the formula for the area of a circle.
You can create a modified version of the formula for the area of a circle, using this relationship between circumference and radius. Use the revised formula to solve the area. Using this revised formula, written with the circumference instead of radius, you can use your given information and find the area directly.
There is nothing wrong with this. You should report your area calculation in that term, or you may approximate it by dividing by 3. The area is approximately equal to sq. Method 4 of Identify the known or given information. In some problems, you may be told information about a sector of the circle and then be asked to find the area of the full circle.
Find the area of Circle O. Define the chosen sector. The space between these two radii is the sector. Measure the central angle of the sector. Use a protractor to measure the central angle made by the two radii. Set the base of the protractor along one of the radii, with the central point of the protractor aligned with the center of the circle. Then read the angle measurement that corresponds with the position of the second radius forming the sector.
The problem you are working on should define this for you. The sum of the small angle and the great angle will be degrees. In some problems, instead of having you measure the central angle, the problem may just tell you the measurement. Use a modified formula for area. Enter the values that you know and solve the area. Report the result.