Is your scale lying to you?
A preset scale like 1/4" = 1' is an assumption: it's only right if the PDF's page is still the true physical sheet size it was drawn at. Plenty of real-world PDFs aren't — they've been "compressed", re-boxed, or re-plotted at a smaller size somewhere along the way. On a half-size page, that preset reports a 10-foot wall as 5 feet, and nothing looks wrong until the bid is.
CountTooling has three layers of defense. Use them.
1. The sheet-size warning (automatic)
When you open the Set Scale presets tab, the app compares the page against standard sheet sizes (ANSI, ARCH, ISO). If the page matches a standard sheet, nothing changes — your preset applies as-is.
If it doesn't match, a yellow warning appears with a sheet picker, defaulted to the app's best guess of what the sheet was originally.
Apply a preset with the picker set, and the scale is corrected by the rescale ratio automatically — the scale label carries the sheet name (e.g. · ARCH D) so you can see the correction was applied. That suffix stays on the sidebar scale readout (1/8" = 1' · ARCH D): it means "corrected as if this page were printed on an ARCH D sheet". Treat it as a standing reminder — whenever you see a sheet-name suffix, verify a known dimension on that page before trusting its numbers.
The correction is still a guess, so a corrected apply now walks you straight into the verify check: the dialog closes and the app asks you to click both ends of a printed dimension to confirm the scale. Esc keeps the applied scale — if the guess was right (a genuinely compressed print of that sheet), you lose nothing. Why it matters: on one sample plan, a wrong ANSI-D guess made a printed 65'-0" wall read 173'-1" — every length 2.67× long, silently. The check catches that in one pass.
If the page truly isn't a standard sheet (a cropped detail, a scanned sketch), pick "Non-standard — don't correct" at the bottom of the sheet picker: the preset applies uncorrected with no check, exactly as on a standard sheet.
2. Verify by measuring (thirty seconds, worth it)
Any time a preset or custom scale is set, a blue advisory in the scale dialog offers Verify by measuring two points:
- Click two points a known distance apart — a dimension line, a door width, a grid spacing.
- Enter the known length.
- The app shows what the current scale reads for that distance, next to the expected value, with the % error — green when it's under 1%.
From there, Keep current scale if it checks out, or Use measured to recalibrate from your two points (the same math as two-point calibration, which is always ground truth).
After Use measured — or any two-point calibration — the scale readout shows the measured line itself (1 ft = 9.0 px) instead of a preset name. That's by design: the scale came from the drawing, not from a chart, so there's no fraction to display — and the dashed reference line stays pinned on the plan where you measured, as the receipt.
3. The on-sheet scale bar (passive check)
For preset and custom scales, the app draws a dashed reference bar of a round length (1 ft, 5 ft, 10 ft…) near the corner of the page — the same "show the scale line on the plan" toggle used by two-point calibration. Glance at it against anything you know on the drawing: if a 10-foot bar spans a 20-foot corridor, the scale is wrong.
This matters most in the one case detection can't catch: a compression that lands exactly on another standard sheet size (a half-size ARCH D is a perfect ARCH B). The warning stays silent — but the scale bar won't look right.
Rules of thumb
- Two-point calibration is immune to all of this — it derives scale from the drawing itself. When a sheet has a trustworthy dimension, prefer it.
- Verify at least one sheet per plan set, and any sheet whose numbers feel off.
- A wrong page scale also flows into scale zones comparisons and every export — catching it early is the whole game.
Related: Setting the scale on a plan covers the three calibration methods themselves.