Print calibration · rev v1
Make a 5 mm grid print at exactly 5 mm
Print one sheet, measure a line on it with a ruler, and type the number in. The correction factor is your expected length divided by your measured length, and it is applied to every PDF you export from here afterwards. It takes about two minutes, it is saved in this browser only, and it corrects uniform scale — the one error that makes technical paper useless.
Print the calibration sheet at 100%
The sheet carries mathematically exact references: one 100 mm line, one 4 inch line, and a 10 mm square in each corner. Any saved correction is deliberately left off this download — it is the baseline you are measuring against.
Exact references on the sheet: one 100 mm line, one 4 in line, and a 10 mm square in each corner — every one labelled with its dimension. Any saved correction is deliberately not applied to this download.
In the print dialog, choose 100% or Actual Size and turn off Fit to page, Shrink oversized pages and borderless. These settings are the single most common cause of wrongly-sized printable paper, and they will corrupt the measurement if left on. Choose the paper size that matches the sheet you downloaded.
Measure the reference and save the correction
Measure between the outer edges of the end ticks. Enter what you actually read, not what you expected — the whole point is the difference between the two.
Expected: 100 mm. Measure between the outer edges of the end ticks.
Correction applied to exports
Reading saved profiles from this browser…
Why you should print a second sheet
A correction you have not verified is a guess with extra arithmetic.
Once a correction is saved and enabled, the verification sheet becomes available above. It is the same reference geometry, but exported with your correction applied — so when you print it at 100% and measure again, the 100 mm line should measure 100 mm. If it does, every paper you export from this site will now be true size on that printer.
If the second sheet is still wrong, the usual cause is that the print dialog applied scaling on one of the two prints. Re-check the settings and start again. If the error flips sign — the sheet is now too large by roughly the amount it was too small — the correction was applied twice, which happens if the driver has its own saved scaling preset.
What calibration cannot fix
Stated plainly, because a tool that claims more accuracy than it has is worse than no tool.
This corrects uniform scale only: the case where the entire page is proportionally too large or too small. It cannot correct any of the following:
- Printer non-linearity— where the error changes across the page, so the first 50 mm and the last 50 mm are wrong by different amounts. If your horizontal and vertical measurements disagree, you have this, and one factor cannot fix it.
- Paper stretch — heat from the fuser and ambient humidity both change paper dimensions slightly, and neither is constant.
- Skew and mechanical feed error — a sheet fed at a slight angle, or a roller that slips, produces distortion no scale factor describes.
- The unprintable margin — most printers physically cannot mark the outer few millimetres of the sheet. Calibration does not move that boundary.
- Print-dialog scaling — the browser, operating system and printer driver can each apply their own Fit, Shrink, borderless expansion or driver-specific scaling after this site has generated the file. No web page can detect or override that; you have to turn it off yourself.
One more deliberate limit: mathematical labels are never distorted to fit. On logarithmic paper, a decade is placed at its true logarithmic position, and on polar paper the radial divisions stay exact. If a label does not fit in the space available, it is omitted rather than squeezed — squeezing would make the sheet lie about its own geometry. The full geometry contract is on the methodology page.
Where your calibration is stored
Your correction factor and any named printer profiles live in this browser’s local storage, on your device. They are never uploaded — there is no server to upload them to. You can export them as JSON for safekeeping, and Reset all removes every trace immediately. Full detail is on the privacy page.
Once a correction is enabled, exports from the Studio, the pack builder and every quick-pick download carry a small note saying so, so a corrected PDF is never a surprise.
Frequently asked questions
Why did my 5 mm grid print at 4.9 mm?
Almost always because the print dialog scaled the page. 'Fit to page', 'Shrink oversized pages' and borderless printing all resize the document, typically by 2–6%. Turn them off and select 100% or 'Actual Size'. If the sheet is still wrong after that, the printer itself is applying a uniform scale, and that is exactly what this page corrects.
How is the correction factor calculated?
Correction = expected length ÷ measured length. If the 100 mm reference line prints as 98.5 mm, the factor is 100 ÷ 98.5 = 1.01523. Every export is then generated 1.01523× larger than nominal, so the printer's own shrinkage of 0.985 brings it back to exactly true size on paper: a 5 mm grid is drawn at 5.076 mm and prints at 5.000 mm.
Does calibration fix every printing problem?
No. It corrects uniform scale only — the case where the whole page is proportionally too big or too small. It cannot fix printer non-linearity, paper stretch from heat or humidity, skew, mechanical feed errors, or the unprintable margin at the edge of the sheet. If your horizontal and vertical measurements disagree, that is non-linearity and no single factor will fix it.
Can the site detect my printer automatically?
No, and any tool claiming otherwise is guessing. A browser cannot read your printer's driver settings or its physical output. The only reliable measurement is the one you take with a ruler on the printed sheet, which is why this page asks you to do it.
Where is my calibration stored?
In this browser's local storage on your device, and nowhere else. It is never uploaded. Clearing the site's data, or pressing 'Reset all' on this page, removes it completely. You can also export your profiles as a JSON file to keep a copy.
Do I need to calibrate at all?
Only if exact physical size matters to you. Many printers are accurate to well under half a percent at 100% scale, which is invisible for note-taking or sketching. Calibrate when you are plotting data, drafting to scale, or checking a measured drawing — and skip it otherwise.