Circle Calculator
Circle calculator: enter the radius to get the area, circumference and diameter in one step, with the pi formulas and working written out for you.
Formula
Area = πr² ; Circumference = 2πr
Use it from the API
curl "https://moltcalc.com/api/calc/circle?radius=5"
See the API docs for every endpoint and the input schema.
FAQ
How do I find the area of a circle?+
Multiply pi by the radius squared: A = πr². A circle with radius 5 has an area of about 78.54 square units.
What is the formula for circumference?+
Circumference is 2πr, or equivalently π times the diameter. For radius 5 that is about 31.42 units.
What if I only know the diameter?+
Divide the diameter by 2 to get the radius, then use the formulas as usual. The diameter is always exactly twice the radius.
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