Geometry

Circle Area & Circumference

Enter the radius or the diameter of a circle. You can keep the answer exact, written as a multiple of π, or round it to a decimal.

InputsA = πr²

Measurement givenValueUnitAnswer form

Step-by-step

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Fill in the fields and press Solve. The full method will appear here, one numbered step at a time.

Find the area and circumference of a circle with radius 7 cm, in terms of π.

1.
Start from the radius given.
```
r = 7 cm
```
2.
The area of a circle is π times the radius squared.
```
A = πr² = π × 7² = 49π cm²
```
3.
The circumference is π times the diameter, which is the same as 2πr.
```
C = 2πr = 2 × π × 7 = 14π cm
```

Answer: Area = 49π cm² · Circumference = 14π cm

Note: Answers can be left exactly in π or rounded; rounded answers are marked ≈.

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The formulas this tool uses, each explained with symbols, conditions and its own example in the Formula Library.