Circle Calculator – Instantly compute area, circumference, diameter, and radius of a circle using simple formulas for quick, accurate geometry and math problem solving.
Enter any one value below and click calculate to find the rest.
The Circle Calculator helps you easily calculate important circle measurements such as area, circumference, diameter, and radius. Whether you’re working on math homework, construction projects, or design tasks, this tool provides fast and accurate results.
✅ Area = π × r²
✅ Circumference = 2 × π × r
✅ Diameter = 2 × r
✅ Radius = d ÷ 2
✅ Can solve for any missing value if at least one is given (radius, diameter, circumference, or area)
Easy input of radius, diameter, or circumference
Provides all circle measurements instantly
Supports decimal and whole numbers
Works in both metric (cm, m) and imperial (in, ft) units
Step-by-step formulas for learning and understanding
📌 Students & teachers learning geometry
📌 Engineers & architects working on design and construction
📌 Designers & artists creating circular patterns
📌 Anyone needing accurate circle calculations
If you only know the circumference, divide it by 2π
to quickly find the radius, then calculate area or diameter easily.
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📏 Percent Calculator – Measure boundaries of 2D shapes