Each complete bento presented on Just Bento has a calorie count. This is derived from the following information:
- Official nutritional information labels on packaged foods
- Online nutrition information databases, such as the ones at Calorie Lab and CalorieKing
- English language nutritional databases often have inaccurate or misleading information about Japanese foods, so I rely on the official food nutrient database (五訂食品標準成分表) which is published by the Ministry of Education, Culture, Sports, Science and Technology and is the standard nutrition information text for dieticianss and other food professionals in Japan. (There are several consumer-friendly versions of this very useful publication available in Japanese. I use one with lots of cute pictures.)
Keep in mind that all calorie counts are approximate, since portion sizes may vary.
Most of the complete bentos (the numbered ones) are around 500 to 600 calories or lower. They can easily be made bigger or smaller just by increasing the volume of each component. (I frequently show larger "Guy" variations.)
Cup measures and weight and such
The capacity of "1 cup" varies from country to country, in a maddening way. In
the U.S. it's about 240ml (236.588238 ml); in Japan it's 200ml; in the UK it's 436ml. I use 240ml (standard U.S. cup measure) as an approximimate middle ground, especially for rice. If you are very concerned about every single calorie, it's best to invest in a good kitchen scale.