Dimension line
A line carrying a measurement: the distance between the two points its ends touch.
How to read it
In the A/E/C Graphics Standard dimension lines show a linear measurement, with the figure above the line and the ends marked by slashes at 45 degrees or filled arrowheads. The Navy's blueprint reading course ends dimension lines in arrowheads.
Also searched as: dimension string.
This explains what a symbol represents on a drawing. Conventions vary between firms and standards, and a drawing's own legend takes precedence.
Differences by trade
The Navy course breaks the dimension line to fit the figure, except in architectural and structural drafting. Architectural drawings to the A/E/C standard keep the line whole, with the figure above it. Older practice broke it too: Wyatt's 1920 textbook describes the usual dimension line as a fine solid line broken for the figure at its centre, with an arrow at each end.
Read next
- Next in Blueprint symbolsConcreteMarks concrete in a section or plan. The dots and small triangles are the conventional pattern for concrete.
- In GD&T symbolsBasic dimensionA number in a rectangle is a basic dimension: a theoretically exact value with no tolerance of its own. The tolerance for the feature it locates or shapes is in a feature control frame.
More blueprint symbols
The same shape elsewhere
Browse symbols drawn with letters and numbers or lines.
Sources
- A/E/C Graphics Standard, Release 2.2, ERDC/ITL SR-23-1, U.S. Army Engineer Research and Development Center, CAD/BIM Technology Center, secs. 4.3, 5.5.1, 5.5.3
- Blueprint Reading and Sketching, NAVEDTRA 14040A, Naval Education and Training Command, U.S. Navy, ch. 2, dimension lines
- Blue Print Reading: Interpreting Working Drawings, E. M. Wyatt, 1920, Bruce Publishing Company, Milwaukee (Internet Archive), Arrows
Researched, edited and approved by Rory Hansen before publishing. Last reviewed September 24, 2026. How we research
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