How to measure a PDF drawing to scale

Why measurements off a PDF go wrong

A scale note like 1" = 20' is only true for the sheet as it was plotted. A few common things quietly break it:

• The PDF was printed or re-saved to a different paper size, for example with "fit to page", so every distance shrank or grew by the same factor.
• The sheet holds more than one scale: a plan at 1" = 20' next to details at 1/4" = 1'-0".
• The set is a scan. A scanned sheet is a picture of lines, so there is no linework to snap to and every click is an estimate.

The fix is always the same: set the scale for the view you are measuring, then check it against a dimension that is printed on the sheet before you trust any number.

Step 1: Set the drawing scale

In Vellum, open the scale control in the status bar, or the drawing settings in the Properties panel. Pick a standard imperial or metric scale, or enter a custom scale equation when the drawing uses a non-standard ratio. From then on the Measure and Area tools report real-world values.

Step 2: Check it against a known dimension

Find a dimension the designer already wrote on the sheet, such as a labeled property line, a grid spacing, or a dimensioned wall, and measure it. If your measurement doesn't match the label, the scale is wrong, and so is every length and area you take from it. Fix the scale first.

Step 3: Measure lengths

1. 1

   Start the Measure tool

   Press M.

2. 2

   Click the points

   Click a start point, then each next point. Vellum shows each segment's length and the running total. Snapping lands your clicks on real endpoints, midpoints, and intersections in the PDF's linework.

3. 3

   Finish

   Press Enter or Esc to end the measurement.

To place a known length instead, type it after the first click: the cursor sets the direction and the typed value sets the length. Feet-inches (4-7), math (4*2), and unit suffixes (3m, 7") all work.

Step 4: Measure areas and perimeters

1. 1

   Start the Area tool

   Press A.

2. 2

   Outline the region

   Click points around its boundary.

3. 3

   Close the path

   Vellum reads the enclosed area and the perimeter.

Step 5: Set units, precision, and readable labels

Choose imperial or metric units and the rounding you want (decimal places or fractional increments) in the drawing settings of the Properties panel.

To make a measurement explain itself, double-click its text and write a label around the value, such as SPAN LENGTH: 24'-6" (TYP. OF 3). The value stays live: it updates if the endpoints, the scale, or the units change.