Drawing scaler

V2 by Guy Rixon, December 2020

Given one known dimension, other lengths can be scaled off an engineering drawing. This page lets you pick the lengths from an image using the mouse and does the calculations for you.

Scaling from scans of line drawings should work well. Scaling from photographs is less reliable because of projection effects (and this page doesn't handle those effects for you).

Choose an image to measure:

Setting the scale: click twice on the image to pick two points a known distance apart, then enter the distance between those points. Repeat until you're happy with the setting, then press "use this scale".

First point: (?, ?) pixels; second point: (?, ?) pixels.

Distance between points: ? pixels → units (any unit, but must be a single number; e.g. inches, or feet, but not feet and inches).

Image scale is currently ? pixels per unit. Use this scale

Applying the scale: click twice to get the scaled distance between pairs of points. If you zoom the browser view to see more detail then you need to set the scale again.

First point: (?, ?) pixels; second point: (?, ?) pixels.

Distance between points: ? pixels → ? units.

Image scale is currently ? pixels per unit. Change this scale