Slide rules HOME page INSTRUCTIONS A-to-Z


A slide rule consists of three basic elements: the main body of the rule, known as the stock (or stator), the movable part, known as the slide, and a moveable cursor (or indicator) made of clear glass or plastic.

On the stock and slide there are marked a number of scales. In the simplest slide rules there may be three or four scales on the stock and two on the slide. On a complex rule there may be a total of twenty or more scales. For an explanation of how to read the scales see here.

Some slide rules have marks on stock and/or the slide. These are known as gauge points and are used to facilitate certain types of calculation.

The cursor has a fine hair line to enable scales which are not adjacent to each other to be used together. Some cursors have more than one hair line, these are also used to facilitate certain types of calculation.

Diagram of slide rule

These elements together are used to perform mathematical calculations.

If you are new to slide rules, look at the section on scales; this will help you identify what the different scales are for. Then look at the section on calculations; this will point you to more detailed information on slide rule use.

Some rules have scales on one face only and a cursor which can only be used on that face; these are referred to as "simplex" rules. Others have scales on both faces with a cursor which can also be used on both faces; these are referred to as "duplex." A very common intermediary between the two forms is found on rules with scales only on one face of the stock but on both sides of the slide. Within this latter group there are two variants; usually a small mark on the back of the stock allows the slide to be used without removing it but some times the slide has to be removed and inserted with face reversed.

There are alternative forms of rules which are circular or cyndrical. These are discussed seperately using examples from my collection.