How to Use an Architect's Scale Ruler

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Things You'll Need

  • Scale ruler(s)

  • Architectural drawing

  • Calculator

  • Drafting paper

  • Mechanical pencil

  • Drafting pen

Scale rulers are typically made of hard plastic or aluminum.
Image Credit: AndreyPopov/iStock/Getty Images

Architects use scale rulers to determine and represent the actual dimensions of large structures such as houses and buildings, and smaller items such as furniture, on a reasonably sized piece of paper. These rulers are either flat or triangular, depending on the number of different scales that must be used. The most common scale measurements are indicated as a ratio of fractions of an inch--or inches--to feet, and read from both left to right and right to left.

Interpreting a Draft

Step 1

Look at each end of the ruler to find the side with the scale used in the drawing you want to measure.

Step 2

Place the ruler along the side of the wall--or item--you want to measure in the drawing, with the zero exactly flush with the end of that side. Note that the zero is not at the end of the ruler, but about a quarter of an inch from the end.

Step 3

Count the number of full increments or "ticks" on the ruler from zero to the end of the line you are measuring to obtain the length in feet. For example, if you are using a 1/4 scale and your measurement is six quarter-inch increments, you know that the actual size of the wall or item you are measuring is 6 feet long. If you are using a 1/8 scale and the line is five major increments long, and half of another major increment, the actual size of the item is 5 feet 6 inches long.

Step 4

Using the small hash marks on the opposite side of the zero to measure the inches for a line that is not exactly flush with a full increment. These lines break down the scale you are using into inches. Slide the ruler so that the last full increment you counted aligns with the end of that line. Then count the number of marks from zero in the opposite direction, up to the beginning of the side of the item you are measuring.

Step 5

Add the number of feet from step 3 and the number of inches from step 4 to obtain the total length of the item's side.

Step 6

Repeat steps 2 through 5 for all subsequent lines you wish to measure.

Drawing With the Ruler

Step 1

Determine the appropriate scale of the item you are going to draw.

Step 2

Place the scale ruler on the drafting paper and use the mechanical pencil to make a hash mark at zero.

Step 3

Determine the end point of the item being drawn by taking the real length of the item in feet. For example, if the item is 10 feet long and you are using a 1/8 scale, the line you draw will be 10 increments, long.

Step 4

Draw a hash mark at the end point, the increment marked "10."

Step 5

Draw a straight line along the edge of the ruler connecting the two hash marks using the mechanical pencil.

Step 6

Repeat steps 2 through 5 for all subsequent sides of the item being drawn.

Step 7

Once the item is completely drawn in pencil, trace over the lines with a drafting pen for permanence.


For each scale, the main increment in each scale has the longest line or "tick"; in a 1/4 scale, the first 1/4 inch is marked "1," representing 1 foot, the second tick is marked "2" representing 2 feet, and so on. Each major number represents the number of feet. The half lines between the major increments represent six inches. A triangular scale holds 12 scales.


Always make sure your pencil tip is extra sharp and use a drafting or fine-point pen; a wide mark could throw off your measurements, and even the smallest of increments on the paper can translate into a major difference in the structure.

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