B5 vs A5: How to Choose Your Planner Size

Planner sizes sound like a small decision. They are not. The size you choose shapes how much you write, where you carry it, and whether you actually keep using it. B5 and A5 are two of the most common sizes, and people mix them up often. Here is what each one is, and a simple way to pick.

The quick version

B5 and A5 are both standard paper sizes. The difference is the footprint.

• B5 measures 176 x 250 mm (6.9 x 9.8 in).
• A5 measures 148 x 210 mm (5.8 x 8.3 in).

B5 is the larger of the two. Side by side, a B5 page gives you noticeably more room to write, while A5 has a smaller, more compact feel. Neither is better. They are built for different jobs.

To picture B5: a sheet of US printer paper is 8.5 by 11 inches, and B5 is a bit smaller at 6.9 by 9.8 inches. Hold up a sheet of printer paper and you are close.

What B5 gives you

B5 is the size Griffin Opus makes today. We chose it on purpose. It is large enough to lay out a real day without crowding, and small enough to carry without thinking about it.

On a B5 page you get room to do actual work. A full daily plan with space left over. Meeting notes that do not run off the edge. A project page you can map out in one view. If you write by hand, or you like to see a whole week or a whole meeting at a glance, that extra width earns its place.

Here is how B5 shows up across the system:

• The Modular Binder. A durable B5 binder built on the Opus Snap Ring. It lays flat, holds up to about 40 sheets, and stays light enough to carry anywhere.
• The Core Inserts. Loose-leaf B5 pages, each with a single job, printed in soft gray so the structure supports your thinking instead of fighting it.
• The Notebooks. The same premium B5 paper in softcover, spiral, and flexbound, for when you want something bound.

The inserts and notebooks are all B5, built around the one binder, so your pages fit and the paper always matches.

Where A5 fits

A5 is the smaller, more pocketable size. If your main goal is to travel as light as possible, or you mostly jot short lists and quick notes, a smaller footprint can feel right. That is a real preference, and it is a fair reason to choose A5.

A quick, honest note: Griffin Opus does not make an A5 size yet. It is on our product roadmap for the future, so it is not something you can buy from us today. We would rather tell you that plainly than pretend otherwise. If a compact size is the one thing you need right now, that is good to know before you decide.

A simple way to choose

Forget the millimeters for a second. Ask yourself three questions.

1. How much do you write? If you fill pages and like space to think, lean toward B5. If you keep things short, a smaller size can work.
2. Where does it live? On a desk, in a work bag, next to your laptop? B5 sits comfortably there. If it has to fit a small purse or a jacket pocket, size matters more.
3. Do you want it to grow with you? This is the real one. A fixed planner locks you into one layout. A modular system lets you swap pages as your work changes, so you are never stuck with a book half full of pages you never use.

For most people doing focused, hybrid work, B5 hits the balance. Big enough to work. Light enough to carry.

One more thing about size

With a bound planner, the size you buy is the size you are stuck with for the year. The Griffin Opus system works differently. The binder stays. The pages move. You can rebuild your setup in seconds, swap a layout that is not working, and add pages as a project grows. You can watch the Opus Snap Ring open and close in a short video over on The System.

So the size question is really two questions. What footprint fits your hand and your bag, and how much freedom do you want to change your mind later. B5 answers the first. The modular system answers the second.

Quick answers

Is B5 bigger than A5?

Yes. B5 (the ISO size) is 176 x 250 mm (6.9 x 9.8 in). A5 is 148 x 210 mm (5.8 x 8.3 in). B5 gives you more room on the page.

What size is the Griffin Opus system?

Everything in the current system is B5, 176 x 250 mm (6.9 x 9.8 in). Large enough to work comfortably, small enough to carry lightly.

Does Griffin Opus make an A5 size?

Not yet. A5 is on our future product roadmap, so it is not available to buy today. The current system is B5.

Can I try the B5 size for free?

Yes. Our free 2027 Year Focus printable prints on US Letter and trims to B5, so you can hold the real size in your hands first.

Which size should I choose?

If you write a lot, like space to plan, and keep your planner on a desk or in a work bag, B5 is a strong fit. If you want the most compact option possible, a smaller size may suit you better.