Online Protractor Tool
A free protractor that runs in your browser. First take or upload a photo. Then line the angle you want up with the centre point, and drag the needle to measure the angle.
How to use the online protractor
- Press Select image and pick a photo. You can also skip this step and use the blank dial on its own.
- In Move image mode, drag the photo so the corner you are measuring sits exactly on the centre of the crosshair. Use the rotation slider and the zoom buttons to line the start of the protractor with the start of the angle.
- Switch to Move protractor and drag anywhere on the dial to rotate the needle onto the second side of the angle.
- Read the measurement in the box in the bottom right corner. The angle slider also gives you precise control to adjust the protractor.
Measuring angles in a photo
When taking the photograph, make sure to be as square-on to the angle as you can. If the phone is tilted, this will distort the angle in the image. Once the photo is uploaded, you can zoom in, rotate or move the image to precisely place the protractor onto the angle that you want to measure.
Ways to use it
- Use the protractor as a backlight to measure the angle on a paper or to trace the desired angle onto a piece of paper.
- Teachers demonstrating how to measure an angle on a projector or an interactive whiteboard.
- Checking angles in photos for DIY, carpentry, sewing, or quilting.
- If you need a physical one instead, download our free printable protractor template and print it on ordinary paper.
Why we made this tool
Most online protractors allow you to create angles, but do not have image uploads. That is fine for showing what a protractor looks like, but not useful for real world measuring. This one lets you take a photo of your desired angle, then move the angle to line it up perfectly with the protractor. As such, you are able to make accurate measurements from a single photo. You can also use the tool as a back light. This lets you also trace your desired angles onto a sheet of paper.
Frequently asked questions
Is the online protractor free?
Yes. The tool is free to use, with no sign-up, no watermark, and no limits.
How accurate is an online protractor?
The geometry is exact, so the accuracy you get depends on how well the angle is photographed. Make sure to be on the same level as the angle and not tilted. This will make sure that the image captures the angle correctly. As long as the angle in the image is correct, then your measured angle will also be correct.
Can I measure an angle without uploading a photo?
Yes. Skip the image step and the blank dial works on its own, which is useful on a touchscreen or as a backlight for tracing an angle onto paper.
How do I measure the angle between two lines?
Rotate the image until one of the lines sits on the horizontal 0 degree axis, then drag the needle onto the other line and read the result.