Slide Rule Basics

how to place the decimal point

Whether you are multiplying 1200 by 4, or 120 by 4, it is all represented as 1.2 x 4 on a slide rule. As the result is read out to be 4.8, where to place the decimal point?

Except for simple cases that you can estimate the results, it’s often difficult, or counter-intuitive to place the decimal point correctly for slide rule calculations.