▣ CALCULATORS Updated July 25, 2026

Circle Calculator

Radius, diameter, circumference, and area.

Radius
Diameter
Circumference
Area
Result
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How it works

Any single known measurement determines the rest, so the tool solves back to the radius first and then derives diameter, circumference, and area.

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Frequently asked questions

Which value should I fill in?

Just one. Fill the box you know and leave the others blank.

What value of pi is used?

JavaScript's Math.PI, accurate to about 15 decimal places.

Comments

Comments aren't enabled yet. When you're ready, this is where a service like Giscus, Disqus, or a custom form would go — the slot is already reserved on every tool page.