How To Read an Architect Scale Ruler

An engineering scale or architect scale ruler is essential for measuring distances for every part of a scaled-down design in an architectural drawing, blueprint or orthographic projection. Scale rulers can combine up to four scales or feature a symmetric cross-section with three lobes and six scales. Follow these three steps to read customary or metric scale rulers.

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1. Inspect the Ruler

The first thing you should notice about standard scale rulers is that one side of these measuring tools is designated for feet, with inches on the other size of the zero. Try to conceptualize a scale ruler as a standard ruler that has been shrunk to fit the blueprints, diagrams or plans you are measuring. Various ends of a scale ruler have measurements based on the most commonly used scales, such as one-eighth, one-quarter, one-half or three-quarters of an inch equals a foot. Be sure that you read the ruler from the appropriate end for the scale of the conceptual drawings with which you are working.

2. Confirm Customary or Metric Units

Depending on the creator or origin of the drawings you are working with, you may need to use a metric ruler marked in centimeters and millimeters. Other than full scale, in which every inch is divided into sixteenths, here are the most common scales for customary measurements, as read from both sides:

Three-inches-to-the-foot or one-and-one-half-inch-to-the-foot
One-inch-to-the-foot or one-half-inch-to-the-foot
Three-quarters-inch-to-the-foot or three-eighths-inch-to-the-foot
One-quarter-inch-to-the-foot or one-eighth-inch-to-the-foot
Three-sixteenths-inch-to-the-foot or three-thirty-seconds-inch-to-the-foot

Metric ratios do not refer back to any set base unit. This means that the scale or ratio of measurement and unit of measurement will both be necessary to interpret plans. An engineering scale features precise, decimalized fractions of an inch, such as tenths, twentieths, thirtieths, fortieths, fiftieths and sixtieths of an inch for use with detailed drawings or working plans.

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3. Cut Out the Calculating

A scale ruler is most useful for eliminating the need to calculate for scale when interpreting blueprints, plans or drawings. Depending on the scale of measurement you are working in, feet and inches will be oriented on different sides. Check the markings on both ends of a scale ruler and make sure that you measure in the right direction to accurately interpret architectural or engineering plans. Students, new contractors, and amateur to novice engineers should learn how to use an engineering scale or architectural scale ruler to obtain accurate measurements. Start by making sure you have the right measuring tool for the job and confirming the scale.