How to use a Slide Rule  

When learning to operate a slide rule, it is convenient to have one...

If you don not own a real slide rule, you can use one of the many simulations of slide rules that have been created.
An online emulation of a powerful Pickett 909 slide rule is available at

In Google Play and the Apple App Store many apps can be found to simulate slide rule, of various quality.
A Digital Slide Rule that works online as well as on a desktop computer or as a mobile app is provided by The Animated Software Company.

Wayne Harrison provides
PDFs for exotic slide rules

You can also make your own paper slide rule.

Look at an English manual (Thornton instruction book on Ron Manley's Slide Rule Site),
or try the following summary:

How do slide rules work? (3.5 × 2 = 7) From high school math classes we remember the following rule for logarithms: Log(a × b) = Log(a) + Log(b) The most commonly used scales (such as the A, B, C and D scales) are logarithmic. A scale value of 3.5 has a length of Log(3.5) = 0.544 units from the starting point (1) of the scale. Likewise, the value 2 has a length 0.301. If we want to calculate 3.5 × 2, we can represent the rule Log(3.5 × 2) = Log(3.5) + Log(2) = 0.544 + 0.301 = 0.845 = Log(7) by placing the logarithms of 3.5 and 2 (the “lengths”) one after the other on the A scale and the B scale respectively. See the following figure in which the result 7 can be read on the A scale as the sum of the two.

Or watch the animation

More examples can be found on Isabelle Saillot's YouTube channel.