Measure from Photo (Photo Ruler)
Measure the real-world size of an object from a photo: calibrate using a known reference (2 points) or a 4-corner rectangle (for angled shots, more accurate).
Measure the real-world size of an object from a photo by using an edge of known length as a scale reference. It can measure distances, perimeters, and polygon areas.
How to use Measure from Photo
- Take or select a photo of the object you want to measure.
- Draw a reference segment and enter its real length (for example, the edge of an A4 sheet = 29.7 cm).
- Draw the points you want to measure to get the distance, perimeter, or area.
Frequently asked questions
Is the result perfectly accurate?
This is an estimate based on a 2D image. Shooting straight-on (perpendicular to the object's plane) and using a longer reference segment gives the smallest error.
Why do I need a known reference segment?
An image doesn't contain real-world size information; the reference segment lets the tool convert pixels into real units (cm/mm).
🔒 Measure from Photo (Photo Ruler) runs entirely in your browser — the data you enter is not sent to any server. Free, no sign-up required. See145 free dev tools more.