Photo measure

Simple, relative length/distance measurements in photo / image files, based on a known reference object size.
Estimate dimensions in a picture right in your browser (no software download, no data is uploaded to the server).
Technical drawings such as floor plans are ideal, because they contain a scale already.
However: No Warranty (please don't blame me if e.g. your kitchen furniture don't fit...)

Note that this method is only good for rough estimates in photos, due to camera perspective (and lens imperfections).
It's best if the reference object and whatever you want to measure are near each other and at the same distance from the camera when you take the picture.