Guide to choosing the right size bento box

So you ordered a bento box online, it arrives and you're shocked at how tiny it is. People try to tell you to just eat less, but you have a sneaking suspicion that you may have accidentally bought a bento box sized for a 2-year-old instead of an adult. Here's how to tell: check the box's total capacity against the gender/age/height guidelines in the table below (I translated them from a popular Japanese website that's been getting a lot of media exposure in Japan -- they're based on official Japanese nutritional guidelines).

In Japan, bento box size is described not by its dimensions (inches or centimeters), but instead by its volume or capacity (in milliliters -- ml).  Why? Because a rule of thumb in Japan is that when you pack a bento box normally (A: 3 parts grain dishes, 1 part protein dishes, 2 parts vegetable dishes; B: without candy, junk food or fatty food; and C: without empty space), calories correspond directly to capacity. So a 600ml box should hold a 600-calorie meal.

Capacity (容量) is usually written on the bento box package and also often on the bottom of the bento box in raised plastic. If you're not sure of your box's capacity, you can measure it yourself by filling the box with water, pouring the water into a liquid measuring cup and checking the milliliters (ml) or ccs there. Most, if not all, Japanese eBay sellers should be able to tell you the size of a box in ml if asked. (Edited to add: 240ml = 1 cup American)