Circle Area & Circumference Calculator
Pi in every calculation.
Circle Area & Circumference Calculator
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Calculated instantly
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What This Calculator Does
The Circle Area & Circumference Calculator computes area, circumference, and diameter from any given dimension. Pi (pi) is the ratio of circumference to diameter.
How It Works
Area = pi x r^2. Circumference = 2 x pi x r. Diameter = 2 x r.
Example
A circle with radius 7: area = pi x 49 = 153.94, circumference = 2 x pi x 7 = 43.98.
Formula
A = pi*r^2, C = 2*pi*rReading the Results
Area
The total space inside the circle, in square units.
Circumference
The distance around the circle.
Diameter
The distance across the circle through the center.
Frequently Asked Questions
What is pi?
Pi is a mathematical constant approximately equal to 3.14159265. It is the ratio of a circle circumference to its diameter.
How do I find area from diameter?
Divide diameter by 2 to get radius, then use area = pi x radius^2.
Is pi infinite?
Pi is an irrational number with an infinite non-repeating decimal expansion. It cannot be expressed as a fraction.