How to Read an Architectural Ruler

An architectural ruler, more commonly called an architect scale, is a device used to draw and study blueprints. In order for blueprints to be practical in size, they usually have to be drawn "to scale," meaning the objects depicted in the blueprint are drawn proportionally smaller than they would appear in real life. In architecture it is crucial that these proportional scales be precise, hence the use for a fixed-dimension ruler in architectural drawing. Once you are familiar with an architect scale, you can use it to quickly convert straight-line dimensional quantities with minimal use of arithmetic.

Things You'll Need

• Architect scale
• Blueprint
• Pencil

Instructions

1. Take out your blueprint and look for the legend. That will contain the scale information. For instance, if a drawing is said to be "1/8 inch = 1 foot" in scale, it means that every inch on the blueprint corresponds to 8 feet in true size, for a ratio of 1:96. (In other words, the real thing would be 96 times longer than what's drawn on the blueprint.)

2. Take out your architect scale and examine it. Most architect scales have three sides, while others are two-sided (i.e., flat). Most of the time, you will find more than one scale on each side. Wherever two scales run together, notice that one scale goes from left to right, and the other from right to left. This is done to pack more scales into a single ruler, while minimizing confusion.

3. Look on the ruler for the scale indicated on the blueprint. For instance, if the blueprint describes a "1/8 = 1 foot" scale, look for the "1/8" scale on the ruler. Once again, be mindful that if the scale is printed on the left side of the ruler, it will go from left to right, and vice versa.

4. Apply your scale to the blueprint, with the "0" point at the beginning of the line to be measured. If your blueprint contains a line representing a wall that runs 4 3/8 inches along the ruler, it means that the real length of the wall is 35 feet.

5. Reverse the process when drawing your own blueprints by first calculating the length of the real object and then scaling it down accordingly. For example, using the "1/8 inch = 1 foot" example, a wall 20 feet in length would become 20/8 inches, or 2 1/2 inches on the blueprint. If your blueprint will be drawn to a different scale, say "1/4 inch = 1 foot," then the same real-world wall of 20 feet would become 20/4 inches, or 5 inches, on the blueprint.

Tips & Warnings

• Make sure you use the correct scale. If you don't, you will either draw or read your blueprint incorrectly.

References

• United States Fired Administration: Using engineer and architect scales