Changing units in SketchUp is a simple matter, but one which can save you hours of frustrating rescaling and double-checking. We show you how in our SketchUp courses. 
From time to time you’ll find it necessary to change your units of measurement. This will happen if you open a model created by an American user – they will generally have used the Imperial system of feet and inches. And it’s therefore necessary to convert the units to Metric, metres or millimetres. Most builders and architects and interior designers use the latter, but town planners and civil engineers may use the larger unit of metres.
This is a really easy matter – simply go to Window > Model Info. Click on the Units section of the left-hand side of the dialog box, and change the Format to Metric and Millimetres (or Metres). Precision: 0 is usually adequate for buildings.
You can then double-check the length of a known line with the Tape Measure tool (T). If it doesn’t correspond, you can type in a new value and hit Enter. SketchUp will ask if you want to rescale the whole model. Hit Yes if it’s a new model; if it has other objects in it you would be better to use the Scale tool for that object only. You’d also have to work out the scale factor: divide or multiply the length by its true length.
Many useful tips and techniques can be found at the SketchUp website. And see many examples of our own clients’ work on our Facebook page.
Other related SketchUp Blog Posts:

• SketchUp background
• SketchUp introduction
• SketchUp modeling
• SketchUp contours
• SketchUp workspace