CTB vs STB for CAD Standards: Which Should You Use?
CTB and STB solve the same plotting problem in different ways. CTB chooses plot behavior from an object's indexed color; STB assigns a named plot style directly to objects or layers. The better choice is the system your team can standardize, exchange and maintain consistently.
Start here — what you are going to do
Your goal: Compare CTB and STB side by side and decide whether your office should keep its current system or plan a controlled migration.
Where to start: Open one representative drawing and check which plot-style mode it already uses.
Beginner rule: Do not convert a live project simply because one system sounds cleaner. First understand the existing templates, consultant files and plotting standards.
Step by step — follow this in AutoCAD
Step 1 — Identify the current drawing mode
Where: Command line > PSTYLEMODE.
Do this: Read the value: 1 means color-dependent/CTB mode; 0 means named/STB mode.
Check: You know what the current DWG actually uses.
Step 2 — Inspect the current Page Setup
Where: PAGESETUP > Modify > Plot Style Table.
Do this: Note the selected .ctb or .stb file.
Check: The drawing’s real plotting standard is visible.
Step 3 — If it is CTB, inspect the color logic
Where: Layer Properties + selected CTB.
Do this: Choose a few office ACI colors and see how color maps to plotted lineweight/color/screening.
Check: You understand the CTB dependency on indexed color.
Step 4 — If it is STB, inspect named styles
Where: Layer Properties / object Properties > Plot Style + selected STB.
Do this: Compare Normal with one or more named styles such as Thin or Heavy.
Check: You understand how STB assigns plotting behavior by name.
Step 5 — Compare an equivalent test output
Where: Calibration drawing or representative sheet.
Do this: Plot the graphical hierarchy under the current standard and, only in a safe test environment, any proposed alternative.
Check: You can compare real output rather than terminology.
Step 6 — Assess migration cost
Where: Templates, existing DWGs, external consultants, training and standards files.
Do this: List what would need conversion or retraining.
Check: The decision includes operational impact.
Step 7 — Keep or migrate deliberately
Where: CAD standards decision.
Do this: If migrating, use test copies and documented conversion procedures before production rollout.
Check: No live project is used as the experiment.
Beginner example
A long-established CTB office may already have reliable layer colors, consultant expectations and calibration sheets. STB can make plot intent more explicit by name, but that advantage must outweigh the cost of converting templates, legacy drawings and team habits.
Understand what AutoCAD is doing
CTB vs STB at a glance
| Question | CTB | STB |
|---|---|---|
| How is the plot style selected? | By indexed object/layer color. | By a named Plot Style assigned to an object or layer. |
| Typical file extension | .ctb | .stb |
| Can two same-color objects plot differently? | Not through different CTB color-dependent styles when they use the same indexed color. | Yes, if they are assigned different named plot styles. |
| What carries plotting meaning? | The color standard plus the CTB mapping. | The assigned named style plus the STB definition. |
| Main standards risk | Users use colors that do not follow the plotting convention. | Users leave objects on Normal or assign inconsistent named styles. |
Neither system fixes inconsistent standards by itself
CTB needs disciplined color use. STB needs disciplined named-style assignment. Templates, Page Setups and team training matter in both workflows.
Useful next guides: CTB Plot Styles · STB Plot Styles · Tell Whether a Drawing Uses CTB or STB · Convert CTB Drawing to STB · Convert STB Drawing to CTB
Common problems and what to check first
| What you see | What may be causing it | Check this first |
|---|---|---|
| CTB file is missing | Drawing is CTB-mode but standards file/path is missing | Check PSTYLEMODE and STYLESMANAGER. |
| STB is not listed | Drawing is CTB-mode or STB file is unavailable | Confirm mode before conversion. |
| Consultant drawing plots differently | It uses another mode/table standard | Identify the source drawing’s PSTYLEMODE and exchange the correct standards file. |
| Migration changes lineweights | Mappings were not made equivalent | Use a calibration drawing and compare before/after output. |
When you need a more repeatable workflow
Choose one documented plotting system per project/office workflow and control the associated table files, templates and Page Setups. If you migrate, keep original files and test representative drawings before broad conversion.
Official Autodesk references
Interface labels can vary slightly by AutoCAD release and workspace. The Autodesk pages below document the core workflow used in this guide.
Frequently asked questions
Which is more common?
Autodesk notes that color-dependent plot styles are the more common of the two, but your existing standards and exchange requirements matter more than popularity.
Can one drawing use CTB and STB at the same time?
The drawing is in one plot-style mode at a time.
Should a CTB office convert to STB?
Only when the benefits justify a controlled migration of templates, drawings, standards files and training.
Explore more in Plot Styles & Lineweights Guide.