# How to use an architect’s scale ruler

## Why do you need a scale rule?

A scale rule is a tool that allows you to quickly and easily determine the dimensions of a blueprint or plan without having to use any math at all. If you have to read lots of blueprints, a scale rule is a vital tool to have.

## What is a scale rule?

It’s a rather odd-looking ruler. A scale rule has three sides, with a different ruler on each side. The first thing you need to know is what kind of scale rule to buy. The scale of the blueprints you need to read will tell you what kind of scale rule to buy. An architect’s scale rule will be useful for scales that are not fractions. A regular scale rule uses fractions like ¼ and ½. These are the fraction of an inch as it relates to afoot.

The first thing you need to do is find the scale on your blueprints. It will generally be in the lower left-hand corner of the page. Example: ¼” = 1 ft When you have located this, find the corresponding scale on the ruler. Each side will have four scales on it, so make sure you have the correct one. If you don’t, all you measurements will be off.

The scale will have a long mark to the left of a zero, which is the beginning of the feet, and several shorter marks to the right of the zero, which represents the inches. Line up the zero mark with the beginning of the section you want to measure. The nearest mark the line passes, is the foot measurement. Often, since the same side will have two scales on it, the marks will alternate one scale and then the other, even to odd.

You must make sure you know which one you should be using. Once you count up the feet, slide the ruler left to meet up the end of the line with the nearest foot mark. The beginning of the line will bleed over the zero mark to the right.

The shorter ‘inch’ mark that the line meets up with, will be the amount of inches you need. The first measurement gives you the feet, the second the inches. No math involved, and after a bit of practice, it will become second nature.

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