Measure Radius
Radius and diameter of circles
Runs in your browser. Files never leave your device.
How to use Measure Radius
- Open an image.
- Click three points on the edge of the circle, or choose “Center and edge”.
- Set a scale for real units, and copy the results or download the annotated image.
About this tool
Find the radius, diameter, circumference and area of round objects in a picture. Click any three points on the edge of the circle, or the center and one point on the edge, and the circle is fitted for you.
- Works on your device. Nothing is uploaded.
- Free, with no sign-up and no watermark.
- No limits on file count or size beyond what your device can handle.
Questions and answers
Why use three points?
Exactly one circle passes through three points, so you don’t need to find the center. Spread the points around the edge for the best accuracy.
Can I measure an oval?
Use the Measure Area tool’s ellipse shape to get the width, height, area and perimeter of an oval.
Is Measure Radius free?
Yes. Every tool on ImgImage is free to use, with no sign-up, no watermark and no limit on how many files you process.
Are my files uploaded anywhere?
No. Your files are processed by your own browser and never leave your device. Nothing you open here is sent to a server.
Does it work on my phone?
Yes. It works in any modern browser on phones, tablets and computers. Large files are processed faster on a computer.