If you have a rice cooker, you know that little measuring cup you’re supposed to use to measure the rice? How big is it? If you lose that little cup, how do you measure your rice?
You can pay as much as $10 for a replacement cup, which is insane given that you can buy a cheap-o rice cooker for $15. You may as well buy a new rice cooker!
However, I have a 3D printer, so the idea of paying anything for a tiny bit of injection molded plastic seems pretty silly.
But the question was how big is that cup? It doesn’t match any other measuring device in the kitchen. It’s close to 3/4 cup, so some rice cooker manufacturers recommend that.
In truth, the important thing is the ratio of rice to water, though it depends on the type of rice (anywhere from 1.25 to 2 parts water to 1 part rice), and there is a fair amount of leeway on the precision.
My rice cooker is a “neuro fuzzy logic” Matsushita model imported from Japan many years ago when smart rice cookers were just becoming a thing in Japan but weren’t yet available in the U.S.. I paid a pretty penny for it, but it gets lots of use and it still works today.
The bowl has markings on the inside to fill water based on the type of rice and number of measuring cups of rice. So the cup is super convenient and it would be a pain to have to measure both rice and water.
So how big is the rice measuring cup? The rice measuring cup is 1 gō, an archaic unit of measurement that is essentially defined as one serving of rice.
The whole system of measurement is called Shakkan-hō, named after two of the primary units: Shaku (length) and Kan (mass). (No relation to the stage name of the singer Chaka Kahn.) It’s derived from a Chinese system that dates from the 13th century BC, and were adopted by Japan in the 8th century BCE. It was abandoned in 1924 for the metric system.
A gō is 1/1000 of a koku. A koku was originally defined as a the amount of rice needed to feed one person for one year. Given something between 2-3 servings of rice per day, a gō is a single serving of rice. Koku was also used to measure the capacity of cargo ships, and to determine taxation.
A koku is about 40 gallons, or 180.4 liters. Which makes a gō 180.39 milliliters, which we can safely round down to 180 ml, which is 0.76 cups or just a smidge over 6 fluid ounces. (This is the size of the original Coca-Cola soda fountain glasses, so you can use one of those for measuring your rice if you want).
Anyway, I used an open source tool named OpenSCAD to design a 3D model for a 180 ml cup and printed it out. I posted it to Thingiverse and YouMagine if you want to download a copy of the OpenSCAD script or the STL model. Here’s what it looks like printed out (filled with long grain brown rice):