How to Set 1″ = 20′ Engineering Scale in AutoCAD
For a drawing that uses decimal feet, 1"=20' means one inch on paper represents twenty feet in the model. Select the named engineering scale in the viewport, lock it, and verify a known distance.
Start here — what you are going to do
Your goal: Create and verify a Layout viewport at 1″=20′.
Where to start: Open the civil/site drawing and the Layout used for issue.
Beginner rule: Change one scale-related setting at a time. After setting a viewport or plot scale, use Preview and verify one known measurement before trusting the final sheet.
Step by step — follow this in AutoCAD
Step 1 — Confirm the model-unit convention
Where: Model Space > measure a known site/civil distance.
Do this: Confirm whether the drawing uses decimal feet or another office convention.
Check: You know what one drawing unit represents.
Step 2 — Open the production Layout
Where: Bottom tabs > choose the sheet.
Do this: Use the actual paper Layout.
Check: The title block and sheet are visible.
Step 3 — Select the viewport
Where: Paper Space > click viewport border.
Do this: Select only the view that needs the engineering scale.
Check: Viewport Scale is available.
Step 4 — Choose the engineering scale
Where: Viewport Scale / Properties > Standard Scale.
Do this: Choose 1″ = 20′ from Standard Scale when available.
Check: The viewport reports 1″ = 20′.
Step 5 — Pan and lock
Where: Inside viewport > PAN; then Display Locked = Yes.
Do this: Frame the view without changing magnification.
Check: The scale remains fixed.
Step 6 — Preview and verify
Where: Ctrl+P > Preview > PDF.
Do this: Measure the verification distance described below in the PDF.
Check: The final measurement agrees with the engineering scale.
Beginner example
A 100-foot line should measure 5 inches on paper at 1″=20′. Use that as a simple verification after creating the PDF.
Understand what AutoCAD is doing
Engineering scale notation is not a metric 1:n label
The notation states how many model feet are represented by one paper inch. Always keep the drawing’s unit convention explicit.
The viewport is still the scale control
The Layout remains the physical sheet while each viewport can carry a different engineering scale.
Civil workflows add more layers
Civil 3D plan production, profile views and annotation standards can add additional scale considerations, but the final viewport still needs to be checked and locked.
Useful next guides: Plot Scale · Viewport Scale · Set a Viewport Scale · Verify Viewport Scale · Civil 3D Printing & Plotting Guide
Common problems and what to check first
| What you see | What may be causing it | Check this first |
|---|---|---|
| Engineering scale is missing | Scale list was customized | Use SCALELISTEDIT and add the verified scale definition. |
| Viewport is wildly wrong | Model is not in expected feet convention | Measure model units before changing scale. |
| Scale changes during navigation | Viewport is unlocked | Restore the named scale, PAN, then lock. |
| PDF is correct but paper is wrong | Viewer/printer applies scaling | Print at Actual Size/100%. |
When you need a more repeatable workflow
For recurring civil or site sheets, document the model-unit convention and the approved engineering scales, keep them available in the office template, lock production viewports, and verify one known site distance in the PDF. That makes 1"=20', 1"=50' and similar scales reproducible across projects and workstations.
Official Autodesk references
Interface labels can vary slightly by AutoCAD release and workspace. These Autodesk pages are the primary references for the workflow above.
Frequently asked questions
What is the difference between architectural and engineering scales?
Architectural scales commonly use fractional inches per foot, while engineering scales commonly use one inch representing a number of feet.
Can one civil sheet use several engineering scales?
Yes. Set and lock each viewport independently.
Should I trust the scale label in the title?
No. Verify the actual viewport setting and a known PDF measurement.
Explore more in CAD Plot Scale: Metric, Architectural & Engineering.