When you are using scales on a drawing, do not confuse the engineer's scale with a metric scale. They are very similar in appearance. You will often find metric dimensions used on blueprints from other countries. Metric drawings are dimensioned in millimeters (mm). There are 25.4 millimeters to an inch. A meter is 39.37 inches, a few inches longer than a yard measure.

Scales of 1:100 and 1:200 are common scales for metric drawings. One millimeter on the drawing represents 100 or 200 millimeters on the actual building.

Metric blueprints developed in the United States are normally marked “METRIC.” In countries that use metric, however, no metric notations are made.