Circle Calculator

Calculate all circle properties

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Enter any one value to calculate the rest.

How to Use Circle Calculator

Enter value

Enter radius, diameter, area, or circumference.

Calculate

Get all circle properties.

Read

See formulas used.

Why Choose AllTools Circle Calculator?

  • ✓ Area calculation
  • ✓ Circumference
  • ✓ Diameter from radius
  • ✓ Arc length
  • ✓ Sector area
  • ✓ Formula display

Why Use This Tool

  • ★ Instant calculations with no server round-trip
  • ★ Completely free with no usage limits
  • ★ No account or registration required
  • ★ Accurate results using standard mathematical formulas
  • ★ Works on any device including phones and tablets

Related Resources

Calculate areas → Triangle calculations → Calculate volumes →

Frequently Asked Questions

What formulas are used? ▼
Area = πr², Circumference = 2πr, Diameter = 2r. All derived from the radius.
What formulas are used? ▼
Area = πr², Circumference = 2πr, Diameter = 2r. All calculated instantly from the radius you enter.
Does this work on mobile? ▼
Yes. All AllTools calculators are fully responsive and work on phones and tablets.

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