Circle Calculator
Calculate the area, circumference, radius, and diameter of a circle instantly. Free online geometry tool for students and professionals.
About Circle Calculator
Instantly calculate the Area, Circumference, Diameter, or Radius of a circle. Simply enter one known value, and we compute the rest with high precision.
Frequently Asked Questions
What formulas are used for these calculations?
We use standard geometry formulas: Area = πr², Circumference = 2πr, and Diameter = 2r.
Can I calculate from Diameter instead of Radius?
Yes, simply enter the value in the Diameter field, and the calculator will automatically derive the Radius and other properties.
What is the value of Pi (π) used?
We use the standard JavaScript Math.PI value (approx 3.14159265359) for maximum precision.
Is this calculator accurate?
Yes, it provides results rounded to two decimal places for readability, but uses high-precision floating-point math internally.
How do I calculate the area of a circle?
Enter the radius or diameter, and the tool will multiply Pi by the square of the radius (A = πr²).
Can I use decimal values?
Yes, you can enter integers or decimals (e.g., radius 5.5).
What units are the results in?
The results are in the same unit system as your input (e.g., if you enter cm, the area is in sq cm).
Is it free?
Yes, this geometry tool is completely free for students, teachers, and professionals.
Do I need to sign up?
No, no registration is required.
Does it show the steps?
Currently, it provides the final answer instantly. We plan to add step-by-step breakdowns in the future.