How to Measure With an Architectural Scale

Take a close look at the scale tool. It should be labeled on the right and left ends with two different scales. For example, it might say 1/8 on the left and 1/4 on the right. The scale tool can be used to read both scales. Each tic from the left, or the 1/8-inch scale, represents one foot. When reading from the right, or the 1/4-inch scale, each tic represents six inches. One set of tics is longer than the other to serve as a guide. Notice that the scale does not start at 0. The tics before the 0 represent inches. Each tic after the 0 represents one foot.

Locate the scale note on the plan. The note should give a numeric scale and a diagram. For example, the note would state the scale is 1/4 inch equals one foot, and it would give an image of an architect's scale that measures one foot long when you measure it with a 1/4-inch scale.

Align the scale tool with the given scale on the plan. Verify that the measurement on the plan lines up with the measurement on the scale tool. Sometimes, printers will change the reproduction size of the plan to fit it on a certain size paper, and this changes the scale of the drawing.

Line up the scale tool with the line to be measured. The 0 should be at the start of the line. Note where the line ends. If it falls between two lines, round down to the nearest number. For example, if the line falls between seven and eight feet, round down to seven feet. Always round down, even if the line is closest to the larger number.

Slide the scale tool so that the number you rounded down to is at the end of the line. The line will then extend past the 0 at the other end. Count the tics in front of the 0. These tics measure inches. If the line ends at the sixth tic, it represents six inches. Add the six inches to the seven feet. This gives you a final measurement of seven feet six inches. It might seem tedious at first, but like anything else, measuring with an architectural scale gets easier with practice.