

It’s hard to get a good number there. Most nutritional measures are by volume or mass, rather than grain count, and the number of grains in a cup or kilo is variable based on type, (un)processed, etc. One site I found says 7k~10k per cup, which would be ~37k/kg. Nutritional calculations are complicated by the conversion from uncooked to cooked because rice usually expands as you cook it, so 1 cup uncooked is fewer grains than uncooked, but nutritional data is usually for cooked foods. Looks like maybe cooking expands the rice by about 3x. Then there are questions regarding what the necessary amount would be. A cup of cooked is ~200 calories. A standard estimate for number of calories needed, ignoring nutrition, is ~2k. Rough guess?
10c cooked rice = 3.33c uncooked = 23k~33k grains




Messed with my chair a fair bit. In terms of getting value for money, building one would probably not be so great. The parts add up quickly, so you usually won’t end up paying less to build than to buy. Best bet is to look for a thrift shop find and maybe upgrade/repair over time.
The most annoying part is how often you go to look for a chair you liked and find out they don’t make it anymore.