Can I find the radius if I only know the perimeter?

Yes, the calculator works both ways. Enter the perimeter value and it will compute the corresponding radius and diameter for you.

Does the tool give the area as well as the perimeter?

Yes, once you input the radius or diameter, the tool automatically calculates and displays the circle's area alongside the perimeter.

Is pi used as exactly 3.14 or is more precision available?

The calculator uses pi approximated as 3.14159265..., which provides standard geometric precision for most practical purposes.

Can I use this for quarter-circles or half-circles?

The tool provides formulas and explanations for quarter-circle and half-circle perimeters in its help section, though the main calculator computes the full circle perimeter.

Geometry & ShapesFree Tool

Circle Perimeter Calculator

Provided byOmni Calculatoromnicalculator.com

This circle perimeter calculator finds the perimeter (p) of a circle if you know its radius (r) or its diameter (d), ...

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Screenshot of Circle Perimeter Calculator on Omni Calculator — omnicalculator.comOpen the live tool →

About this tool

What Circle Perimeter Calculator does

This tool calculates the perimeter (circumference) of a circle when the user provides either the radius or the diameter. It instantly returns the perimeter value and also displays the area, allowing users to solve for multiple circle properties from a single input. The calculator works bidirectionally, meaning users can input a known perimeter to find the radius or diameter, making it useful for both forward and reverse calculations.

Step by step

How to use the Omni Calculator Circle Perimeter Calculator

1
Enter the radius or diameter value in the respective input field
2
The perimeter and area are automatically calculated and displayed below
3
Use the perimeter value to work backwards and find the radius or diameter if needed
4
Click 'Clear all' to reset the calculator for a new calculation

Is it right for you

Best for

Students, teachers, or anyone needing quick, accurate circle perimeter calculations without manual formula work, especially those who want to also see the area or convert between radius, diameter, and perimeter.

Limitations

Results use an approximation of pi (3.14159...)
No option to switch between different units of measurement
Designed for simple circles and does not handle elliptical or complex shapes

Questions

Circle Perimeter Calculator FAQ

Can I find the radius if I only know the perimeter?: Yes, the calculator works both ways. Enter the perimeter value and it will compute the corresponding radius and diameter for you.
Does the tool give the area as well as the perimeter?: Yes, once you input the radius or diameter, the tool automatically calculates and displays the circle's area alongside the perimeter.
Is pi used as exactly 3.14 or is more precision available?: The calculator uses pi approximated as 3.14159265..., which provides standard geometric precision for most practical purposes.
Can I use this for quarter-circles or half-circles?: The tool provides formulas and explanations for quarter-circle and half-circle perimeters in its help section, though the main calculator computes the full circle perimeter.

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