SMJ Pro — Structured monthly journaling in dot-grid | smjpro.com
Four page sizes cover almost every dot-grid notebook; the right one depends on how many rows your layouts need and how far the notebook travels.
The ISO 'A' series halves with each step, so A6 (105 x 148 mm) is exactly half of A5 (148 x 210 mm), which is half of A4 (210 x 297 mm). B5 (176 x 250 mm) sits between A5 and A4 and is a common size for journals that stay on a desk.
Rows are the currency of a monthly log. On a 5 mm dot grid, usable rows equal page height divided by five, minus margins: A6 gives roughly 24-27 rows, A5 about 38-42, B5 around 44-48, and A4 about 52-56. A 31-row monthly log fits any of them, but on A6 the calendar consumes nearly the whole page.
On narrow screens, swipe or scroll the plate sideways.
Page count converts directly into months. At one dated entry per day, divide the page count by 31: a 249-page notebook lasts about 8 months, a 124-page notebook about 4. Index pages and the future-log spread consume a few pages up front, so treat the result as an upper bound.
Paper weight does not change with size. Across all four formats, notebook paper runs 52-120 gsm: 80 gsm is the standard weight, and 90 gsm is the threshold where fountain-pen bleed-through stops being a problem.
Rule of thumb: A5 for a first monthly log, B5 if your daily entries run long, A6 only for a pure capture notebook, A4 for project logs that never leave the desk. The setup steps for the log itself are on the How to Set Up a Monthly Log page, and ruling trade-offs are compared in Dot Grid vs Lined Paper.
Further reading