I’ve started using A4 paper for my note taking. I fell into it almost by accident. I found a cool Rhodia pad to take notes on. Good paper, and it felt good on the nib. Eventually, I found an article that explained how the whole ISO paper system worked, and it is really quite cool. Given to like cool things, especially those that are easy to do and impact no one else, I’ve decided to use A4 for all my personal note taking.
The whole ISO series of paper, and, for that matter, most things in Europe, is based on the metric system (a cool thing we should use (save for measuring Guinness (always measured in pints)) but don’t). A4, the paper that most closely maps to US letter sized paper, is 29.7 cm tall by 21 cm wide, or 11.7 by 8.3 inches.