Planner Refills and Inserts: Which Size Do You Actually Need?

Planner sizes are a naming problem more than a measuring one. Personal, Pocket, A5, A6, Junior, Half Letter, Classic, Compact — some of those describe the same sheet of paper, some are unique to one brand, and none of them tell you what you actually want to know, which is whether your week will fit on the page.

Here is every common size with real dimensions, how much writing each one holds, and a way to choose that does not involve buying three planners to find out.

Every planner insert size in one table

Two notes on that table. A4 is 210 x 297 mm and is not the same sheet as US Letter — it is narrower and taller, so a Letter insert in an A4 binder overhangs at the sides. And "Personal" is the odd one out: at 95 x 171 mm it is narrower than A6 but much taller, which is why Personal inserts look wrong in every other binder.

The question that actually decides it

Not "which is prettiest". This one: how many lines do you write on a normal Tuesday?

Most people badly overestimate. Go and look at last week in whatever you are using now — phone notes, a diary, the back of an envelope. Count the lines. That number, not the aesthetic, is what should pick the size, because a planner with more space than you fill reads as failure every time you open it, and a planner with less space than you need gets abandoned in February.

Roughly what fits on a weekly spread

These are approximate and depend on the layout, but the ranking holds. If you counted six lines on a normal Tuesday, A5 is comfortable and Letter is a lot of white space.

Pick by what you are doing with it

It lives in a bag and gets opened standing up

A6 or Pocket. Anything bigger needs a surface to write on, and a planner you cannot use while standing at the school gate is a planner you update later, which means never.

One planner for work and home

A5 or Half Letter. This is where most people end up, and it is not a coincidence — it is the largest size that still fits in a normal bag, and the smallest that holds a real day.

It sits on a desk and never moves

Letter, Big or Classic. If portability is not a constraint, stop paying for it. The extra width is what makes hourly columns and multi-person layouts work.

A budget binder

A6, and it is not really a choice. A6 is the size that holds bills flat without folding them, which is the entire reason it became the cash-budgeting standard.

A journal or reading log rather than a schedule

A5, Half Letter, or a 5x7 notebook. Long-form writing wants width more than height, and a narrow page turns every paragraph into a column.

Same size, different binding

Size and binding are separate decisions, and mixing them up is why people buy inserts that do not fit. A5 exists in both rings and discs. Half Letter exists in both. The paper is identical; the holes are not.

Ring spacing also differs between sizes, so a Personal insert will not fit a Pocket binder even though both are ring-bound. Always match the size name, not just the system.

Before you buy a year of refills

Print or buy one month in the size you think you want and use it for four weeks. That is the whole test, and it costs almost nothing.

What you learn in those four weeks is not "is this pretty" but "did I run out of room on Wednesdays" and "did I carry it". Both of those are unanswerable in a shop and obvious after a month. A year of refills bought on a guess is the most common way people end up with three abandoned planners in a drawer.

Where to go next

If you have landed on discs, discbound planner inserts: sizes explained covers printing and punching your own, and disc compatibility covers which brands interchange.

Still deciding on the system rather than the size? Disc-bound vs ring binder vs spiral is the post for that, and converting a ring binder to disc-bound covers switching without starting over.

Discs are in planner discs, ready-made books in disc-bound notebooks, and A6 cards for budget binders in A6 budget binder inserts.