Vladislav Bronin shares his method of scaling objects without calculating a scale factor.
"At work there are many metric drawings or site measurements in metric units that should be put on drawings with imperial units. Or another case, you have to downscale details on your drawing, let's say, in 1.77 times. Here the headache starts.
"You search for calculators, open AutoCAD internal calculator, write the number down on paper to type it in your commands... Grrr …But there is an old, good, but forgotten trick. Let’s say, you have a measured size of one of your objects equal to 187.65 millimeters and you need to scale it down to inches. Type Scale command, select the desired object, specify the base point, and when the computer prompts for scale factor, type 18765/2540.
"The little complexity is that during the Scale command you can't do arithmetic actions with noninteger numbers. Therefore, you have to multiply both numbers by 10s to get both integers. Or, if we'll return to detail downscaling by 1.77, this will be written just as 100/177 (instead of 1/1.77). Less unnecessary actions, less headaches, and more accurate work."
NOTES FROM CADALYST TIP PATROL: This is a great tip that I have used for a long time too. Do your math in the scale factor. It works great on changing text sizes that are set for one scale factor, but now you need it for another. For example, let’s say your text was drawn for a scale factor of 1:80. Now you need to make the text for a scale factor of 1:30. You can do the math and then enter the scale factor, but with Vladislav’s tip, all you need to do is start the scale command and type in 30/80. How do you know which scale factor is the numerator or the denominator? The scale you want the object to be at goes on top (30 in our example) while the scale the object is goes on the bottom (80 in our case.) think of it as new scale divided by old scale.