Find a different angle.
Place three points to measure an angle. The middle point is the vertex. Add a photo if you need a reference.
A place for a little precision.
Align your object with the ruler.Drag the handles to mark both ends.
Measure twice.
Make once.
Set your scale
Place B at the corner, then A and C along the two sides. No calibration needed.
Find your edges
Drag the points to the ends of your object. Use arrow keys for careful adjustments.
Keep the details
Switch units, save a measurement, or export your list for the project ahead.
Measure an angle with an online protractor
Move B to the corner of your angle, A along the first side, and C along the second side. The readout shows the smaller interior angle from 0 to 180 degrees. You can use a local photo as the background. Screen calibration is unnecessary for angles; image perspective can still affect the apparent angle.
A few small answers.
Better measurements start with knowing your tools.
Is this ruler actual size?
Only after you calibrate it to your screen. The initial scale is an estimate. Match a known physical length using Calibrate screen, then check against another object.
Can I measure an object in a photo?
Yes. Use Photo ruler, upload an image and mark a known reference length. Then mark the distance you want. Both objects must be in the same plane; perspective and lens distortion can affect the result.
Does my image leave my device?
This tool processes the selected image locally in your browser. No image upload service or third-party analytics is included.
What if I change my zoom or monitor?
Calibrate again. We flag detectable screen setting changes, but cannot reliably identify every external display. Check the ruler against a known object whenever your setup changes.
Can I use inches and fractions?
Yes. The inch ruler has sixteenth-inch ticks. Its secondary readout shows a fraction rounded to the nearest sixteenth, alongside metric conversions.