Circle Calculator
By Sagar Kumar · Updated 23 October 2026
Enter any one value — radius, diameter, circumference or area — and get all the others instantly.
| Radius | — |
| Diameter | — |
| Circumference | — |
| Area with π = 22/7 | — |
Circle formulas
Circumference C = 2πr = πd
Area A = πr²
r = C ÷ 2π = √(A ÷ π)
π (pi) ≈ 3.14159. Many school problems use π = 22/7.
Quick examples
| Radius | Circumference | Area |
|---|---|---|
| 1 cm | 6.28 cm | 3.14 cm² |
| 7 cm | 43.98 cm | 153.94 cm² |
| 10 cm | 62.83 cm | 314.16 cm² |
| 14 cm | 87.96 cm | 615.75 cm² |
हिंदी में समझें
वृत्त का क्षेत्रफल = πr² और परिधि = 2πr। जैसे त्रिज्या 7 सेमी हो तो क्षेत्रफल = 22/7 × 7 × 7 = 154 वर्ग सेमी और परिधि = 2 × 22/7 × 7 = 44 सेमी।
Frequently asked questions
What is the area of a circle with radius 7 cm?
Area = πr² = 3.14159 × 7 × 7 ≈ 153.94 cm². Using π = 22/7, the area is exactly 154 cm².
What is the formula for the circumference of a circle?
Circumference = 2πr = πd, where r is the radius and d the diameter. For r = 7 cm, it is about 43.98 cm (44 cm with π = 22/7).
How do I find the radius from the area?
r = √(Area ÷ π). If the area is 154 cm², r = √(154 ÷ 3.14159) ≈ 7 cm.
Should I use 22/7 or 3.14 for π?
Use whatever your teacher or exam asks for. 22/7 gives neat answers when the radius is a multiple of 7; 3.14 or the calculator value of π is more accurate.
What is the difference between radius and diameter?
The diameter goes right across the circle through the centre. It is twice the radius: d = 2r.