Scale Calibration
Accurate measurements depend on correct scale calibration. This guide covers how to calibrate your drawings.
Why Calibration Matters
PDFs and images don't inherently know their real-world scale. A line that's 100 pixels long could represent 1 foot or 100 feet depending on how the drawing was created and exported.
If your scale is wrong, ALL measurements will be wrong. Always verify calibration before starting a takeoff.
Using the Calibration Tool
Shortcut: C
Step-by-Step
-
Find a known dimension on your drawing:
- Dimension lines with measurements
- Standard door widths (typically 3'-0")
- Parking spaces (typically 9'-0" wide)
- Grid lines with known spacing
-
Press
Cor click the Calibrate tool in the toolbar -
Click the start point of your known dimension
-
Click the end point of your known dimension
-
Enter the real-world distance in the calibration dialog:
- Type the number (e.g., "3")
- Select the unit (ft, in, m, cm)
-
Click Apply - the scale is now set
Common Known Dimensions
Use these standard dimensions when no explicit dimension lines are available:
| Item | Typical Width |
|---|---|
| Interior door | 3'-0" (36") |
| Exterior door | 3'-0" (36") |
| Double door | 6'-0" (72") |
| Garage door (single) | 8'-0" to 9'-0" |
| Garage door (double) | 16'-0" to 18'-0" |
| Parking space | 9'-0" wide |
| Standard ceiling height | 8'-0" to 9'-0" |
| Standard stair width | 3'-0" to 3'-6" |
Verifying Your Calibration
After calibrating, verify accuracy by measuring something else you know:
- Use the Linear tool (
4) to measure another known dimension - Compare the measurement to what it should be
- If it's wrong, recalibrate using a different reference point
Some drawings have different scales on different sheets. Calibrate each sheet individually for best accuracy.
Scale Formats
BuildVision AI understands common architectural scale formats:
| Format | Ratio | Use Case |
|---|---|---|
| 1/4" = 1'-0" | 1:48 | Floor plans |
| 1/8" = 1'-0" | 1:96 | Site plans |
| 1" = 1'-0" | 1:12 | Details |
| 1:100 | 1:100 | Metric plans |
| 1:50 | 1:50 | Metric details |
Troubleshooting
Measurements seem way off
- Recalibrate using a different known dimension
- Check if you're on the right sheet (scales vary by sheet)
- Verify the PDF wasn't scaled when exported
Can't find a known dimension
- Look for dimension lines in corners or margins
- Check title blocks for scale information
- Use door widths as fallback (most are 3'-0")
Scale keeps resetting
- Scale is stored per document page
- Switching pages may require recalibration
- Each sheet can have its own scale
Pro Tips
Multiple Scales on One Sheet
Some drawings show overall plans and enlarged details on the same sheet. Calibrate to the area you're measuring - don't calibrate from a detail if you're measuring the main plan.
Verify with Multiple References
For critical takeoffs, calibrate using one reference and verify with another. If measurements match expected values, you're good.
Save Time with AI Scale Detection
BuildVision AI can often detect scale automatically from title blocks and dimension lines. Check if auto-detect worked before manual calibration.