3 free online calculators with step-by-step solutions
Pick the right tool for your problem — 2D shapes, 3D solids, proofs, or composite figures.
Start with these essential circle calculators calculators
Every circle reduces to one constant — π (≈ 3.14159) — and one length: the radius. From there, the canonical formulas A = πr², C = 2πr, and d = 2r generate every other measurement you need. The calculators below cover area, circumference (also called perimeter), diameter, radius, and the trickier secondary geometry: arc length, sector area, chord length, segment area, inscribed angles, tangent properties, and analytic circle equations in (x − h)² + (y − k)² = r² form. Inputs are interchangeable — give the calculator the area, it returns the radius; give it the diameter, it returns the circumference. For step-by-step working with formula derivations, click "AI Solve" on any circle tool.
This collection has 3 circle calculators: 1 are tagged Most Popular, 2 are supporting tools. The most-used tools include Circle Geometry Calculator.