NTS Doesn’t Mean Scale Doesn’t Matter

Mar 11

NTS stands for Not to Scale, but it does not mean scale is irrelevant. In construction documents, geometry and dimensions may be intentionally non-scaled, yet annotation, text height, and linetypes must still follow strict scale logic to remain legible, consistent, and buildable. Across the AEC industry, a widely accepted convention is a 3/32-inch plotted text height in paper space. That single standard governs how text and symbols are sized in model space, particularly in CAD and BIM environments that rely on scaled or annotative text.

When scale discipline breaks down, the result isn’t just messy drawings. It leads to: illegible field sets, inconsistent annotation between sheets, missed notes during construction, and RFIs driven by visibility, not design intent. In short: NTS protects intent, but scale protects communication.

Why 3/32” Became the Standard

A 3/32" plotted text height strikes a practical balance, but mainly that text is: readable in half-size field prints, compact enough for dense coordination drawings, and familiar to reviewers, contractors, and inspectors. Whether annotation lives in paper space or model space, the goal is the same: everything should plot at 3/32” on paper, regardless of drawing scale.

The Formula Behind Text Height

Model-space text height follows a simple relationship between drawing scale and plotted size:

(12 ÷ Drawing Scale in inches) × Plotted Text Height = Model Space Text Height

Example: 1/8" scale × 3/32" text = (12 ÷ 0.125) × 0.09375 = 9" model-space height

That’s why 9-inches appears so frequently in CAD standards for 1/8" scale plans; it isn’t convention, it’s math.

Typical Annotation Scaling Reference

The values shown below assume a target plotted text height of 3/32-inch, with annotation placed in model space and scaled relative to the drawing’s view scale. Linetype scale is selected intentionally for legibility rather than strict mathematical equivalence, with LTSCALE typically set to approximately one-half of the plot ratio, consistent with common MEP drafting standards. Paper space and model space linetype scaling are assumed to be enabled so that dashed and centerline patterns plot consistently across viewports and sheet sizes.

  
    
  
      Drawing Scale
      Model Space Text Height
      Plot Ratio
      Relative LTSCALE
    

  
      1/16" = 1'-0"
      18"
      1:192
      96
    

      3/32" = 1'-0"
      12"
      1:128
      64
    

      1/8" = 1'-0"
      9"
      1:96
      48
    

      3/16" = 1'-0"
      6"
      1:64
      32
    

      1/4" = 1'-0"
      4.5"
      1:48
      24
    

      3/8" = 1'-0"
      3"
      1:32
      16
    

      1/2" = 1'-0"
      2.25"
      1:24
      12
    


  

Paper Space vs. Model Space (Quick Clarification)

With paper space annotation, text and symbols are placed directly at the intended plotted size, with text heights set to 3/32-inch and viewport scale controlling only the geometry shown. This approach minimizes scaling calculations and simplifies quality control, as text and symbols appear consistently regardless of the drawing scale used in each viewport. Linetype behavior is primarily managed through paper space settings, reducing the risk of inconsistent dashed patterns between sheets.

With model space annotation, text and symbols are placed within the model and scaled relative to the drawing’s view scale using calculated text heights. This method requires that annotation scale, text size, and viewport scale remain aligned to ensure legibility. When implemented consistently, model space annotation scales cleanly across multiple sheets and viewports, but it demands disciplined standards to avoid mismatches that can result in unreadable or inconsistent drawings.

Most drafting issues arise when paper space and model space annotation methods are mixed without a clear standard, leading to conflicting scale logic and unpredictable plot results.

The Takeaway

NTS exists to prevent false dimensional assumptions, but scale is what ensures drawings remain legible and consistent across sheets and print sizes. Text height, in particular, is not a matter of preference, it is governed by math and by industry standards intended to support clear communication. Good drawings do more than convey design intent; they make that intent readable and usable at every scale. At Aethera Engineers, maintaining scale discipline is one of the ways we reduce friction between design and construction and support smoother project delivery.

AutoCAD Variable … a Technical Appendix

For teams working in AutoCAD-based workflows, the following system variables directly support the standards discussed above:

Variable	Purpose	Typical Setting	Notes
TEXTSIZE	Controls default model-space text height	Per scale (e.g. 9" @ 1/8")	Derived using the text-height formula
ANNOTATIVEDWG	Enables annotative objects in the drawing	1 (On)	Must remain consistent across sheets
DIMSCALE	Scales non-annotative dimensions	1	Annotative dimensions preferred
LTSCALE	Controls model-space linetype scale	≈ ½ plot ratio	Selected for legibility, not math purity
PSLTSCALE	Controls paper space linetype scaling	1	Ensures consistent linetypes through viewports
MSLTSCALE	Controls model space linetype scaling	1	Required for annotative workflows

Together, LTSCALE, PSLTSCALE, and MSLTSCALE determine whether dashed and center lines read correctly on printed plans.

Michael Reise https://www.aethera.io