Circle Calculator
Enter any one measurement of a circle to get all the others. Add a central angle to get the arc length, sector area and chord.
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Area
- Radius
- Diameter
- Circumference
- Area
- Arc length
- Sector area
- Chord length
- Segment area
- Work
Saved Calculations
Items you add are saved in this browser.
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Circle Formulas
d = 2r C = 2πr = πd A = πr²
r = C ÷ 2π r = √(A ÷ π)
Arc = r × θ (radians) Sector = ½ r² θ Chord = 2r sin(θ/2) Segment = ½ r² (θ − sin θ)
θ in radians is degrees × π ÷ 180. The segment is the sliver between the chord and the arc.
Worked Example
Tips
π ≈ 3.14159265. Doubling the radius doubles the circumference but quadruples the area, which is why a 16-inch pizza has almost twice the pizza of a 12-inch one (201 vs 113 square inches).