Find any circle measurement from any other.
Circumference C = 2πr and area A = πr². For radius 7 the area is 153.938040026.
A circle is fully described by one number. Enter the radius, diameter, circumference or area and this calculator returns the other three; add an angle and it also finds the arc length, sector area, chord length and segment area for that part of the circle.
π ≈ 3.14159265358979 is used at full precision. For other shapes see the Area Calculator, Volume Calculator (cylinders, spheres) and Surface Area Calculator.
The calculator applies the standard method step by step.
| Item | Value |
|---|---|
| Radius (r) | 7 |
| Diameter (d = 2r) | 14 |
| Circumference (C = 2πr) | 43.9822971503 |
| Area (A = πr²) | 153.938040026 |
| Arc length (θ in degrees) | 10.9955742876 |
| Sector area | 38.4845100065 |
| Chord length | 9.89949493661 |
| Segment area | 13.9845100065 |
| Radius | Circumference |
|---|---|
| r = 3 | C = 18.8495559215 |
| r = 5 | C = 31.4159265359 |
| r = 7 | C = 43.9822971503 |
| r = 10 | C = 62.8318530718 |
| r = 25 | C = 157.079632679 |
r = C ÷ (2π). A circumference of 31.416 gives a radius of 5.
A = π × (d ÷ 2)².
The distance around it: C = 2πr = πd.
A 'pizza slice' of a circle between two radii. Its area is θ ÷ 360 × πr².
A straight line joining two points on the circle. The diameter is the longest chord.
The ratio of a circle's circumference to its diameter — about 3.14159 for every circle.
It uses the standard method: C = 2πr A = πr² arc = rθ sector = ½r²θ The full working and a worked example are shown on this page.
Decimal results use standard double-precision arithmetic (about 15–16 significant digits). Tools that work with whole numbers — big numbers, factors, bases, combinations — use exact integer arithmetic, so no digits are lost.
Yes for checking your work and learning the method. The steps and formula are shown so you can understand the answer, but follow your teacher's rules about calculators in exams.
No. Everything is calculated in your browser and nothing you enter is uploaded or saved.
