Circumference of a Circle
1. Start with the formula: Circumference = 2?r. Don't forget: ? is pi (? ) and 2?r = 2 ? ? ? r. The circumference of a circle is calculated using the formula: 2 x ? x radius, where ? is a mathematical constant, equal to about It was originally defined as the ratio of a circle's circumference to its diameter (see second formula below on why) and appears in many formulas in .
The three primary characteristics of a circle are its circumference, diameter and radius. All circles share common properties that allow for formulas that relate these characteristics to one another. For example, the famous number pi approximately 3. It is also true that a circle's circumference has a specific relationship with its radius, and this means that there is a simple formula for calculating the radius of a circle if you know its circumference.
The circumference of a circle is the distance around a circle's edge. It is what you draw if you use a standard pin-and-pencil compass to draw a circle around a central point.
The circumference of any circle is directly proportional to the diameter and the radius of the circle. The radius of a circle is a line drawn from the direct center of the circle to its outer edge. A radius can be drawn in any direction from the central point.
A circle's radius is exactly half the length of the same circle's diameter, which is a line that divides the circle into two equal halves. The definition of pi reveals the equation for the circumference of a circle. Pi is equal to the circumference of a circle divided by its diameter. In mathematical terms this looks like the following:. And since the diameter of a circle is twice as what happens if the euro collapses as its radius, you can substitute 2r for d, with r standing for radius.
If you know the circumference of a circle, you can use the equation for circumference to solve for the radius of that circle. First you have to rearrange the equation to solve for r.
Do this by dividing both sides by pi x 2. This operation will cancel on the right side of the equation and leave r by itself. If you then flip the sides of the equation, it will look like this:.
Suppose you know that the circumference of a circle is 20 centimeters and you want to calculate the radius. Just plug the value for the circumference into the equation and solve. Remember that pi is approximately equal to 3. Tim Banas started writing professionally in after teaching high school science for seven years. You get the equation for circumference by solving for C in the equation above. How to Find the Radius of a Semi Circle. How to Find the Radius. How to Convert Circumference to Diameter on a Calculator.
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How to Find the Perimeter of a Circle. Copyright Leaf Group Ltd.
How to calculate the circumference of a circle?
If you know the diameter or radius of a circle, you can work out the circumference. To begin with, remember that pi is an irrational number written with the symbol ?. ? is roughly equal to The formula for working out the circumference of a circle is: Circumference of circle = ? x Diameter of circle. The formula to calculate the circumference if you know the radius is as follows: Circumference = 2 x Radius x ? ? = Pi = , thus, the math to calculate the circumference of a circle with a radius of is: 2 x x = And the answer to the circumference of a circle with a radius of is approximately: ? ? = Pi = Enter the circumference which is the total length of the edge around the circle, if it was straightened out. This is the radius of a circle that corresponds to the specified circumference. The radius is the distance between the centre and any point on the outer edge of a circle.
Use this calculator to easily calculate the circumference of a circle, given its radius in any metric: mm, cm, meters, km, inches, feet, yards, miles, etc. It was originally defined as the ratio of a circle's circumference to its diameter see second formula below on why and appears in many formulas in mathematics, physics, and everyday life. In practical situations it is often easier to measure the diameter instead of the radius.
Calculation is easy once you have measured the circle's radius or diameter, using the formulas above or, if you prefer the easier way - using our circumference of a circle calculator above. To make sure you are measuring the diameter correctly, it should be the biggest measurement you can get.
If by moving the measurement instrument slightly you get a bigger diameter size, then go with that. One needs to know just the radius or the diameter of a circle in order to calculate its circumference. If the radius is given, applying the formula is straightforward. For example, the circumference of a circle with a radius of 4 inches is simply 2 x 3. If the diameter is given instead, first divide it by two, then repeat the above process.
The circumference is therefore 2 x 3. Circles are often used by architects for athletic tracks, recreational areas, buildings, and roundabouts. The famous Ferris-wheel is a circle. Circle-like parts, e. The invention of the wheel-cart was one of the transforming events in early human history.
If you'd like to cite this online calculator resource and information as provided on the page, you can use the following citation: Georgiev G.
Calculators Converters Randomizers Articles Search. Circumference of a Circle Calculator Use this calculator to easily calculate the circumference of a circle, given its radius in any metric: mm, cm, meters, km, inches, feet, yards, miles, etc.
Circle radius. Calculation results Circle circumference Share calculator:. Embed this tool! Related calculators Perimeter calculator Perimeter of a rectangle Perimeter of a triangle Perimeter of a square. The calculation result is in the unit in which you measured the circle radius or diameter. How to calculate the circumference of a circle?
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