3.8 Scaling a picture to life

A picture arrives at a placeholder width, which is almost never its real one. Set scale… in the inspector fixes that in two clicks and a number: click two points on the picture whose real separation you know — a dimension line, a door width, a column grid — and type what they actually measure.

Two points clicked on the plan's dimension line, a dashed measurement between them reading 5.077 m, and a box asking for the real distance — Figure 3.8 Calibrating against the drawing’s own dimension line. The two clicks land on its end ticks, the dashed measurement reads what the picture *currently* spans — 5.077 m, because it arrived at a placeholder width — and the box takes the number the drawing prints beside it: **12.00 m**. Type it, press `Enter`, and the plan is life size.

The plane then rescales uniformly about the first point you clicked. That anchor matters: it is what lets you calibrate a plan you have already positioned without it walking off where you put it. The resize and the compensating move go into the document as a single change, so one Ctrl+Z puts back both.

What you calibrate is what you clicked

The number you type is the distance between those two points, not the width of the picture. A dimension line that measures a 12 m room across a sheet with margins leaves the picture wider than 12 m — correctly so. Pick the longest known distance you can see: the same half-millimetre of click error spread over 12 m is a tenth of the error it is over 1 m.