This tool allows you to adjust the size of the model with relation to real-world measures. The tool will first measure a bounding box for your model. The X, Y, and Z box measurements are shown both in the viewport and in the Dimensions box.

Dimensions: Change the numeric values for one of the measures to re-scale the object. For example, if you want the height of your object to be 10 cm, you could enter 10 cm for the Y coordinate, and the model would be uniformly scaled to accommodate. Similarly, if you change the units from cm to mm, the object will change with respect to the rest of the scene.

This example shows a bunny model that we have set to be 10 cm tall in a MakerBot Replicator 2:

And now a 2 inch tall bunny in the same print bed:

 

Set From Measurements: Another way to set the size of an object is to specify how large you want an individual feature to be. This mode allows you to draw a line segment on the model and specify how long that segment should be in the real world. The rest of the model will then be scaled proportionally.

In this example we’ve specified that the bunny’s ear should be roughly 2 inches long:

 

To achieve this we first click-and-drag with the left mouse button to specify a line segment on the model. In this example we've drawn the line segment on the bunny's ear. We then specify the length of this line segment in the Set Target Length box. The bunny is rescaled so that the ear is roughly 2 inches long.

You can add multiple measurements to the object and specify a length for each one. Since it may not be possible to satisfy all measurements with one uniform scaling, we report the Real Length after attempting to enforce all measures. The Avg Deviation and Max Deviation outputs report how close we got to satisfying all measures.