SHAPES, DATA, AND SCHOOL MATH
Calculate the area, circumference, and diameter of a circle using a radius and the standard value of pi.
Your result
Enter your values and select Calculate. Your result stays on this device.
Area = πr²; circumference = 2πr; diameter = 2r.
The figure is a perfect circle and the radius uses one consistent linear unit.
This circle calculator combines the three most common circle searches in one focused page. Enter the radius once to get area, circumference, and diameter.
Use case
Enter a radius once and calculate πr², 2πr, and 2r together for a transparent geometry check.
Find a circle’s area, circumference, and diameter from one radius.
Build a reliable scenario
Circle Calculator helps you check a specific geometry & statistics question with figures that apply to you. Calculate the area, circumference, and diameter of a circle using a radius and the standard value of pi. Enter a radius once and calculate πr², 2πr, and 2r together for a transparent geometry check. Find a circle’s area, circumference, and diameter from one radius. The page keeps the method and limits visible so the result can be understood, compared, and checked instead of treated as an unexplained answer.
Prepare Radius. Measure or enter the radius from center to edge. Keep the radius in the unit you want returned. Calculate the area, circumference, and diameter. Round only after matching the precision required by your assignment or project. Keep units, dates, currency, and time periods consistent.
The stated method is: Area = πr²; circumference = 2πr; diameter = 2r. Change one assumption at a time to see which input drives the result, then compare scenarios on the same basis.
The figure is a perfect circle and the radius uses one consistent linear unit. Check the input and rounding, then calculate again.
Method and update
Last reviewed: 2026-08-22. This tool performs the stated formula locally in your browser using the values you enter.
Square the radius and multiply by pi.
Multiply the radius by 2 and by pi.
Yes. The diameter passes through the center and equals two radii.
Keep exploring
Clear calculation guide
This free Circle Calculator keeps the values and the calculation method visible instead of returning an unexplained number. Calculate the area, circumference, and diameter of a circle using a radius and the standard value of pi. Use it to check a scenario with the figures that apply to you.
Start by checking units, dates, decimal places, and the option you selected. This circle calculator combines the three most common circle searches in one focused page. Enter the radius once to get area, circumference, and diameter. The stated mathematical method is: Area = πr²; circumference = 2πr; diameter = 2r.
Change one assumption at a time to understand what moves the result, then keep any final record or institution-specific rule separate from the arithmetic. The figure is a perfect circle and the radius uses one consistent linear unit. Hesaplayın is a clear, browser-based calculator for checking the maths behind your decision.