TechTools

Circle Calculator

Circle Properties

Radius (r)

5.000000 cm

Diameter (2r)

10.000000 cm

Circumference (2πr)

31.415927 cm

Area (πr²)

78.539816 cm²

Sector Calculator

Arc Length

7.8540 cm

Sector Area

19.6350 cm²

Annulus (Ring) Area

Ring Area = π(R² − r²)

50.2655 cm²

Circular Segment Area

Segment Area = ½r²(θ − sin θ)

2.2647 cm²

π to 15 decimal places

3.141592653589793

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Enter radius, diameter, circumference, or area to get all others instantly. Sector area, arc length, annulus area, and segment area. Unit conversion included.

How to Use

  1. 1Enter any one known value: radius, diameter, circumference, or area
  2. 2All other values are calculated and displayed instantly
  3. 3Scroll down for Sector: enter angle in degrees to get arc length and sector area
  4. 4Use Annulus: enter inner and outer radius to get ring area
  5. 5Select units (mm, cm, m, in, ft) and all values convert automatically

Features

  • Input any one: radius, diameter, circumference, or area
  • Calculates all 4 values instantly
  • Sector: arc length and sector area for any angle
  • Annulus area (inner and outer radius)
  • Unit selector (mm/cm/m/in/ft)
  • π shown to 15 decimal places
  • 100% browser-based

Frequently Asked Questions

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