justyourcalculatorCircle Calculator
Know one measurement of a circle? Get all the others instantly.
- 100% Free
- Instant Results
- No Sign Up
Circle Calculator
Radius, diameter, circumference and area
Area
78.53981634 m²
- Radius (r)
- 5 m
- Diameter (d = 2r)
- 10 m
- Circumference (C = 2πr)Exact: 10π
- 31.4159265359 m
- Area (A = πr²)Exact: 25π
- 78.5398163397 m²
How it was calculated
- r is given
- d = 2 × 5 = 10
- C = 2 × π × 5 = 31.4159265359
- A = π × 5² = 78.5398163397
More Math Calculators
View all calculators- Area CalculatorArea of rectangles, triangles, circles and more
- Volume CalculatorVolume of 11 common 3D shapes
- Surface Area CalculatorSurface area of 11 common 3D shapes
- Distance CalculatorDistance in 2D, 3D, or between two lat/long points
- Triangle CalculatorSolve any triangle from three known values
- Scientific CalculatorTrig, logs, powers, roots and memory in one keypad
- Percentage CalculatorPercent of, percent change and more
- Fraction CalculatorAdd, subtract, multiply and divide fractions
- Standard Deviation CalculatorPopulation or sample standard deviation with steps
- Calculators
- 204+
- Free to use
- 100%
- Results as you type
- Instant
How the circle calculator works
A circle is fully described by one number. The radius r is the distance from the center to the edge, the diameter is twice that, the circumference (perimeter) is 2πr, and the area is πr².
Working backward: r = d / 2, r = C / (2π), and r = √(A / π). π (pi) is about 3.14159265 and is the ratio of any circle's circumference to its diameter.
Using and checking your result
Published by JustYourCalculator. Check the units and assumptions above, and compare a known example before relying on the output. Calculations use browser arithmetic and may round displayed values.
Share links may contain your input values. Anyone with the URL can read them; avoid sharing sensitive personal or financial information.