How to Read Engineering Drawings

Engineering drawings are typically used as visual tools in the creation of homes, bridges, and other buildings. While these drawings can be quite straightforward to individuals who are skilled in the field of engineering or architecture, they can be quite difficult to interpret for laypeople. Knowing how to read engineering drawings will help provide you with a better idea of the building plans.


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    Familiarize yourself with the scale of the drawings.
    • Understanding how large or small certain items are essential when reading engineering drawings. While most engineering drawings are created in "scale" versions of 1/4-1/8 inches (.55-.275 centimeters) per foot, other scales may be used for very large creations. Always determine the scale of the drawing before examining it in detail. If the scale is not obviously evident on the drawing, consult with the engineer who drew it for clarification.
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    Understand the basic symbols used in the engineering drawings.
    • As these drawings are done on such a small scale, the use of symbols is often required. While many symbols exist, understanding a few of the basics can be very helpful when reading engineering drawings. Some of the most common symbols used in these drawings include rectangles, circles, and triangles. As with determining the scale, consulting with the engineer who created the drawing can provide great insight as to the symbols used.
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    Look for circled numbers.
    • As discussed previously, engineering drawings are typically done on a scale so small that creating detail is almost impossible. Because of this, engineers often add circled numbers to certain parts of the drawings. These circled numbers indicate that the area identified is shown in greater detail on another page.
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    Identify specific abbreviations.
    • Abbreviations are a useful tool for engineers. Like symbols, they can indicate shapes, processes, and even dimensions through a few letters. Some of the most common abbreviations used in engineering drawings include DP, which stands for depth, and DIA, which stands for diameter.
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    Work with colleagues.
    • When all else fails, consult with other professionals to better clarify the drawings. While it may be embarrassing to admit that you are having difficulty interpreting the drawing, those who regularly work with and understand the drawings will help you read them. Ask "in the know" individuals on the project to clarify anything you do not understand; better that this happens in the early stages of a project than to encounter a mistake farther into a project because of improperly reading engineering drawings.