I'm happy to say that I hear from folks who have just recently received their first-ever Mini planner. I also hear from people who are looking to get one and haven't seen one in person.
I remember when I purchased my first one, the dimensions of course tell you the size, although when you receive the delightfully shrunken tiny mini planner and see it for yourself for the very first time, it's quite irresistible. But I digress...
Here are some side-by-side examples of a few everyday items that might help give you a feel for the size of the Mini planner size.
First up, side by side with a US dollar bill:
Next, the ever-popular Sharpie marker:
Now with a gigantic iPhone 6 Plus:
For contrast, here's the much smaller Blackberry Q10 phone:
And this is a 3"x5" index card. Surprisingly, this photo seems to skew the scale. If you look closely at where the planner is resting on the surface, you can see slightly better that the index card is taller than the mini.
I hope this is useful and thank you for reading! :)