B6 vs A5 vs B5 Planner Sizes: Which Fits Your Bag
By MUJI USA | Published: 2026-10-13
Category: Comparisons
Compare B6, A5, and B5 planner sizes on portability, writing room, and layout so you can pick the one that actually fits your bag and your week.
Quick answer
For most people, the right planner size is the largest one you will actually carry. A B6 is the easiest to slip into a small bag, an A5 gives you noticeably more writing room for weekly planning, and a B5 is best if you work at a desk and want space for notes, habit tracking, or daily journaling. If you carry a bag daily, start with B6 or A5; if your planner mostly stays on a desk, choose B5.
What actually changes as the size goes up
Planner size affects three things: how much you can write in a single block, how much context you can see at once, and whether the planner leaves your bag. The jump from B6 to A5 is usually the most noticeable for weekly planning because the extra width makes horizontal weekly spreads easier to read and write in. The jump from A5 to B5 is more about having room for side notes, habit trackers, or mini daily entries without squeezing them into the margins.
How to check your bag before you buy
Measure the inside of your everyday bag before choosing a size. A planner that fits the bag but leaves no room for a phone, wallet, or keys will end up staying home. If you switch bags often, a smaller planner is more likely to come with you. If you keep one bag and a desk routine, a larger size is easier to justify.
- Small crossbody or purse: B6 is the safer choice.
- Tote or backpack with a laptop: A5 usually fits without crowding.
- Desk or briefcase: B5 gives you the most writing space.
Weekly layout matters as much as size
Two planners can be the same size but feel very different depending on the weekly spread. Vertical weekly layouts are better for time blocking by the hour, while horizontal weekly layouts are easier for task lists and topic-based planning. Many MUJI planners include optional guides on the weekly spread, so you can divide your day into thirds or separate tasks by topic. That flexibility often matters more than a few millimeters of paper.
Paper, cover, and extras to weigh
If you carry a planner in a bag with a water bottle or coffee, a vinyl cover is a practical detail because it protects against accidental spills and stains. A pocket for cards or folded paper is another small feature that can make a planner more useful day to day. These details are not size-dependent, so check them alongside the dimensions rather than assuming a larger planner is automatically more durable.
Size trade-offs at a glance
- B6: portability first: Easiest to carry in a small purse or crossbody bag. The trade-off is less room for long notes or detailed weekly planning. Choose B6 if the planner only helps when it is with you.
- A5: balanced everyday size: More writing space than B6 while still fitting most totes and backpacks. The trade-off is that it takes up more bag space than a B6. Choose A5 if you want one planner for both bag and desk.
- B5: maximum writing room: Best for weekly spreads, habit tracking, and side notes. The trade-off is that it is less likely to fit in a small bag. Choose B5 if your planner mostly stays on a desk.
Planner options in this size range
- B5 Half Size Monthly/Weekly Planner From Dec. 2026 - White Gray: B5 Half Size Monthly/Weekly Planner with vertical Monday-start weekly spreads and grids to divide your day into thirds or separate tasks by topics. The B5 size gives you the most room for weekly planning, notes, habit tracking, or mini daily journal entries, which suits a desk or a large bag.
- B6 Vertical Monthly/Weekly Planner From Dec. 2026: B6 Vertical Monthly/Weekly Planner made with high quality paper, a vinyl cover, and a pocket for cards or folded paper. The B6 size is the most portable option here, and the vinyl cover and pocket make it easier to carry in a small bag without worrying about spills.
- A5 Monthly/Weekly Planner From Dec. 2026 - Mon. Start: A5 Monthly/Weekly Planner with horizontal Monday-start weekly spreads on the left pages and grid pages on the right for extra notes or habit tracking. The A5 size is a middle ground: more writing room than a B6, but still likely to fit in a tote or backpack.
- B6 Monthly/Weekly Planner From Dec. 2026 - Mon. Start: B6 Monthly/Weekly Planner with horizontal Monday-start weekly spreads on the left pages and grid pages on the right for extra notes or habit tracking. This is the smaller horizontal option, so it suits people who want a portable planner but prefer task lists over hourly vertical planning.
Which planner size should you buy?
Best for
- People who carry a small purse or crossbody bag and need a planner that comes everywhere
- Anyone who prefers a compact weekly overview with grid pages for notes
Not for
- People who need large daily writing space or detailed project notes
- Anyone who wants a planner that stays open on a desk all day
