A graphic scale, also called a scale bar or bar scale, is a ruler drawn on the sheet: a bar divided into lengths such as 0, 5, 10 and 20 feet, or 0, 1, 2 and 5 metres, at the drawing's scale. Unlike a written scale such as 1/4" = 1'-0" or 1:100, it stays correct when the sheet is printed smaller, enlarged or viewed on screen, because the bar shrinks and grows with the drawing. That is why many owners and agencies require one on their sheets, and why it is the most reliable way to measure a drawing whose print size you cannot trust.
Graphic scale, written scale and ratio
| Type | Example | Still true after resizing? |
|---|---|---|
| Written (verbal) scale | 1/4" = 1'-0" | Only at the original sheet size |
| Ratio (representative fraction) | 1:100 | Only at the original sheet size |
| Graphic scale | A bar marked 0, 4, 8, 16 ft | Yes, at any size |
As Penn State's cartography course puts it, "unlike representative fractions, graphic scales remain true when maps are shrunk or magnified." The same holds for construction drawings. Our guide to architectural scales explains written and ratio scales in detail.
Who requires a graphic scale
- The US General Services Administration lists "Graphic scale" among the minimum contents of a sheet title block in its PBS CAD Standard, next to the written drawing scale and the sheet size.
- Transportation agencies often go further: the Minnesota DOT Metro District's designer notes say "All scales shown should be bar scales."
- City site plan checklists commonly ask for a north arrow and a graphic scale together; some ask for the graphic scale and the written scale "in close proximity".
Even where nobody requires it, a graphic scale costs nothing and protects every reader of a reduced print or a PDF.
How to read a graphic scale
- Find zero. On many bars zero is not at the left end. The short segment to the left of zero is subdivided into smaller units (for example feet within the first 5 feet); the main divisions run to the right.
- Read the units written on the bar: feet, metres, or both.
- Measure the distance on the drawing with dividers, a strip of paper or a ruler, then lay it along the bar starting at a whole division right of zero, and read the remainder in the subdivided segment.
- Check the written scale against the bar. If they disagree, the sheet has been printed at a different size; trust the bar.
Half-size sets and the reduced print trap
Many projects print half-size sets for site use. When a 22 x 34 inch (ANSI D) sheet is printed on 11 x 17 inch (ANSI B) paper, the reduction is exactly 50%: a drawing at 1/4" = 1'-0" becomes 1/8" = 1'-0", and the written scale is now wrong by half while the graphic scale is still right. When a 24 x 36 inch sheet goes onto 11 x 17, the reduction is not exactly half (the 11-inch side limits it, to about 46%), so the result is no standard scale at all. Some US transportation departments, the New York State DOT among them, standardised on 22 x 34 sheets so that half-size prints come out at exactly half scale. With a graphic scale on the sheet, either print can still be measured. See drawing sheet sizes for the sheet sizes.
Measuring on a PDF with the graphic scale
A PDF can be shown at any zoom, so a written scale tells you nothing about the size on screen. PDF tools measure in two ways:
- Set a scale ratio: tell the tool the drawing is 1:100 or 1/4" = 1'-0". This works only if the PDF page is still at its original size.
- Calibrate: click both ends of a known length and enter its real value. The graphic scale is the ideal known length: use its longest division, then check the calibration against a written dimension elsewhere on the sheet.
Some PDFs exported from CAD software carry their scale inside the file, and Acrobat can read it. But if the PDF has been resized, combined or printed to PDF again, that embedded scale may no longer match the page, and calibrating on the graphic scale is the safe check. Calibrate again for every view with a different scale, and after any crop or page size change.
NTS: not to scale
A view marked NTS is deliberately not proportional: a diagram, a schematic, or a detail drawn to explain rather than to measure. Never measure an NTS view. Written dimensions govern; if a dimension you need is missing, ask the designer rather than scaling it. Many drawings also carry a general "do not scale drawings" note even when they are drawn to scale, because paper and prints change size; our guide to general notes explains why.
Adding a graphic scale in AutoCAD, Revit and ArchiCAD
- AutoCAD Architecture includes bar scale annotation tools on its annotation tool palette. In plain AutoCAD there is no stock scale bar; offices use their own blocks, often annotative or dynamic so one block serves several scales.
- Revit has no built-in graphic scale that follows the view scale automatically. The usual workaround is an annotation family with one type per scale, or a view title family that includes the bar for each scale.
- ArchiCAD users place a graphic scale object in the view, or add it through the drawing title, depending on the version and template. A bar placed directly on a layout does not know the drawing's scale, because layouts are at 1:1.
Metric and imperial bars
A metric bar is usually divided into whole metres with the first metre subdivided (for example at 1:100: 0, 1, 2, 5, 10 m). An imperial bar is divided into feet with the first segment in smaller parts (at 1/4" = 1'-0": 0, 4, 8, 16 ft). International projects sometimes show both, one above the other.
Frequently asked questions
What is a graphic scale on a drawing?
A bar divided into real-world lengths at the drawing's scale, used as a ruler to measure the drawing at any print or screen size.
Why use a graphic scale instead of a written scale?
Because it stays correct when the sheet is reduced, enlarged or viewed on screen; a written scale is only correct at the original sheet size.
Is a scale bar still accurate if the drawing is printed smaller?
Yes. The bar shrinks with the drawing, so measuring against it gives the right length.
How do you read a scale bar?
Find zero, measure the distance on the drawing, lay it along the bar from a whole division right of zero, and read the remainder in the subdivided part to the left of zero.
What does NTS mean on a drawing?
Not to scale. Do not measure the view; use the written dimensions.
In Ncored, the desktop PDF editor we built in our architecture studio for drawing sets from AutoCAD, Revit, and ArchiCAD, you can set a sheet's scale as a ratio or calibrate it by clicking both ends of a known length, such as the graphic scale, then measure lengths, polylines and areas (metric units) and apply one scale to every sheet in one click. It runs on Windows and Mac (Apple Silicon). 14 days free. No signup, no email, nothing to enter.
Related: architectural scales explained, drawing scale calculator, print drawings to scale.
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