Method
How we measure
Every sheet is laid out in millimetres and written into the PDF in points, at exactly 72 points to the inch. Nothing is scaled in between. That is the whole basis of the claim that a 5 mm square measures 5 mm on paper. This page sets out the arithmetic, the page boxes, the line weights and the tolerances, so you can check the claim rather than take it on trust.
From a millimetre on screen to a point in the file
A PDF has no notion of millimetres. Its coordinate system is the DTP point, defined as exactly 1/72 of an inch, and an inch is exactly 25.4 mm. So a millimetre is 72 divided by 25.4, which is 2.834645 points. Every coordinate you set here is multiplied by that constant and written straight into the file, with no rounding step of our own.
You can verify the result without opening the drawing code. These are the page boxes in the PDFs this site produces, read back out of the generated files:
| Page | MediaBox in points | Same size in mm | Same size in inches |
|---|---|---|---|
| A4 portrait | 595.28 x 841.89 | 210 x 297 | 8.268 x 11.693 |
| A4 landscape | 841.89 x 595.28 | 297 x 210 | 11.693 x 8.268 |
| US Letter portrait | 612 x 792 | 215.9 x 279.4 | 8.5 x 11 |
| US Letter landscape | 792 x 612 | 279.4 x 215.9 | 11 x 8.5 |
Letter comes out as whole numbers of points because it is defined in inches: 8.5 inches is exactly 612 points. A4 does not, because it is defined in millimetres by ISO 216, and 210 mm is 595.2755... points. Both are written at full floating point precision, so the rounding in that table is ours for readability, not the file's.
Why Fit to page breaks the measurement
A print dialog set to Fit to page, Shrink to fit or Shrink oversized pages multiplies the whole page by one factor before it reaches the paper. The factor is whatever it takes to make the source page fit inside the destination sheet's printable area, and it is applied to your grid as much as to the margins.
| Situation | Scale applied | A 5 mm square becomes |
|---|---|---|
| A4 PDF fitted onto Letter paper | 94 percent (279.4 / 297) | 4.70 mm |
| Letter PDF fitted onto A4 paper | 97 percent (210 / 215.9) | 4.86 mm |
| Any page, printer shrinks to its margins | typically 94 to 97 percent | 4.70 to 4.86 mm |
| Printed at 100 percent | none | 5.00 mm |
None of those errors are visible on screen and none of them are announced. That is why the fix is to generate the PDF in the size of the paper in your tray and print at 100 percent, rather than letting the printer resize a page it was never given. The print settings guide walks through the dialog options by name.
Margins and the printable area
No consumer printer prints to the edge of the sheet. Most inkjets and laser printers hold back roughly 5 mm on three sides and a little more at the trailing edge, and anything drawn inside that band is simply not put on the paper. The page margin control therefore starts at 8 mm rather than 0: below that limit a sheet that looks right in the preview would come out with its outer lines missing.
Every generator also keeps its content strictly inside the margin you set. Grids are clipped to the margin box rather than drawn past it, which is why hexagon and isometric sheets end on a cut edge instead of a half cell hanging over the border.
Line weights, and why they are not hairlines
A line has to survive a 300 or 600 DPI printer without disappearing or blotting. These are the weights used, in millimetres:
| Element | Weight | Reason |
|---|---|---|
| Grid, ruling and staff lines | 0.20 mm | Visible on paper, still lighter than a pencil line |
| Dashed midline on handwriting paper | 0.15 mm | Reads as a guide rather than a line to write on |
| Handwriting baseline | 0.35 mm | The line letters sit on, so it leads the row |
| Cornell and planner frames | 0.30 to 0.40 mm | Separates zones without competing with the ruling |
| Sudoku box borders | 0.70 mm | Three by three boxes must read at a glance |
The default line colour is a light warm grey. That is deliberate: it stays behind your own pencil or pen, and it still prints legibly in greyscale or draft mode, which is where most of these sheets end up. If you need a bolder page, the colour control takes any value.
Check it yourself
Tick Include a 100 mm scale ruler before you download. The sheet then carries a 100 mm bar at the foot of the page, marked every 10 mm, drawn inside the margin box rather than in the margin itself so no printer can clip it. Print the sheet and put a ruler on the bar:
- It measures 100 mm. The page printed at true scale, and every grid on it is the size you asked for.
- It measures about 94 mm. An A4 page was fitted onto Letter paper. Regenerate the PDF in Letter.
- It measures about 97 mm. A Letter page was fitted onto A4. Regenerate the PDF in A4.
- Anything else. Your print dialog is scaling for its own reasons. Set it to 100 percent or Actual size.
Tolerances, honestly stated
The arithmetic in the file is exact to floating point, so the PDF is not the source of error. Everything that can go wrong is downstream: the print dialog rescaling, paper stretching slightly with humidity, and the mechanical accuracy of the paper feed, which on a home printer is typically a few tenths of a millimetre across a page. A 100 mm bar that measures between 99.5 and 100.5 mm is a correct print. Anything outside that is a settings problem, not a rounding problem.
Frequently asked questions
How much does Fit to page change my grid?
It depends on the mismatch. Fitting an A4 page onto Letter scales it to about 94 percent, which turns a 5 mm grid into a 4.70 mm grid. Fitting Letter onto A4 scales to about 97 percent, turning 5 mm into 4.86 mm.
Why is the smallest page margin 8 mm?
Because almost no home printer can put ink closer than about 5 to 6 mm from the paper edge. A margin under that limit produces a sheet whose outermost lines are silently clipped, so the control does not offer it.
How do I check a printed sheet is true to size?
Tick Include a 100 mm scale ruler before you download. The sheet then carries a measurable 100 mm bar at the foot of the page. Measure it: if it reads 100 mm the whole page printed at true scale, and if it does not, your print dialog rescaled the page.
Does the screen preview match the PDF exactly?
The preview is drawn from the same numbers but rendered as SVG, so on screen it is scaled to fit your window. Only the PDF carries real measurements; treat the preview as a layout check, not a ruler.
Sources
- ISO 216, the international standard defining the A and B paper series, published by the International Organization for Standardization, for the A series dimensions.
- Markus Kuhn, University of Cambridge, International standard paper sizes, for the history of the standards and the A4 to Letter scaling factor.
- ISO 32000-1 (PDF 1.7), for the default user space unit of 1/72 inch that every coordinate above is expressed in.
Who builds this
PrintNook is built by FusionStudios, a Dutch web studio that makes fast, privacy-friendly web tools. If you need something similar, get in touch.