Cooking from a Japanese recipe, and why the cup is the only hard part
Japanese recipes use a 200 millilitre cup and spoons of 15 and 5 millilitres. The spoons are the metric ones already in your drawer, so they need no conversion at all. The cup does, and the obvious conversion, scaling by volume, misses the mark on 10 of the 16 ingredients we hold.
Start with what does not need converting
A Japanese tablespoon, osaji, is 15 millilitres and a teaspoon, kosaji, is 5. Those are the metric sizes, identical to German, British and New Zealand spoons and within one percent of an American one, so every spoon quantity in a Japanese recipe transfers directly. The full comparison, including the Australian spoon that does not match, is on tablespoon sizes by country. Japanese recipes also write cc where a European writes ml, and the two are the same thing.
That leaves the cup, and Japan has two of them. The kitchen cup is 200 millilitres. The go, the cup that ships in a rice-cooker box, is 180, and the numbered lines inside the cooker bowl count go rather than cups; our rice master takes that apart, and both sit alongside the world's other cups on cup sizes around the world.
Why multiplying by 0.85 does not work
Every English page that covers this hands you the volume ratio: a Japanese cup is 0.85 of an American one, so scale the grams down by that and carry on. We hold measured Japanese figures for 16 ingredients, from the Kagawa Nutrition University standard tables, so the arithmetic can be checked rather than assumed. It misses by more than a few percent on 10 of them, and it misses in both directions.
| Ingredient | US cup | Scaled by volume | What Japan measured | Error |
|---|---|---|---|---|
| Bread crumbs | 108 g | 91 g | 40 g | -56 % |
| Cocoa powder | 86 g | 73 g | 90 g | +23 % |
| Sour cream | 230 g | 194 g | 160 g | -18 % |
| All-purpose flour | 120 g | 101 g | 110 g | +9 % |
| Rice (uncooked) | 185 g | 156 g | 170 g | +9 % |
| Granulated sugar | 198 g | 167 g | 180 g | +8 % |
| Rolled oats | 89 g | 75 g | 80 g | +7 % |
| Cornstarch | 128 g | 108 g | 100 g | -7 % |
| Butter | 227 g | 192 g | 180 g | -6 % |
| Powdered sugar | 113 g | 96 g | 100 g | +4 % |
| Table salt | 292 g | 247 g | 240 g | -3 % |
| Milk | 244 g | 206 g | 210 g | +2 % |
| Honey | 339 g | 287 g | 280 g | -2 % |
| Yogurt | 245 g | 207 g | 210 g | +1 % |
| Almond flour | 96 g | 81 g | 80 g | -1 % |
| Water | 237 g | 200 g | 200 g | 0 % |
Scaled column is our arithmetic on the US figure; measured column is the Japanese tables.
Read that against the standard the rest of this site uses. We call a two-gram gap on a two-hundred-gram cup of sugar agreement, so anything within about three percent counts as the ratio working, not failing. By that measure 6 of the 16 land close enough: water exactly, since a millilitre of it weighs a gram in any country and it is the ruler on our water master, and a handful more within a gram or two. The ratio still fails outright on the other 10, by up to 56 percent, because the Japanese tables weighed each ingredient in a 200 millilitre cup rather than calculating it from anyone else's. Ten misses out of sixteen is a broken method, and calling the near-hits hits rather than inflating the count is what keeps that verdict honest.
Three of the biggest errors are not measurement at all
Look at the top of that table and the largest gaps are not the tables disagreeing. They are different products sharing an English name. Bread crumbs is the clearest: a Japanese cup holds 40 g because Japanese パン粉 is panko, dried in large flakes with air between them, while the American figure of 108 g is fine dry crumbs. No conversion connects them, because they are not the same ingredient, and our breadcrumb master shows the charts agreeing on panko across both traditions once you compare like with like.
Two more traps work the same way. A Japanese recipe saying sugar usually means 上白糖, johakutou, a moist fine sugar that is not granulated sugar; our sugar master puts the silent error at about a third. And 片栗粉, katakuriko, is potato starch, not cornstarch, running roughly a third heavier per cup than the cornstarch beside it in the same Japanese table, which our cornstarch master reads directly from both. Flour has the same shape of problem without the name clash: Japanese flour is graded by protein into 薄力粉 and 強力粉 with no equivalent to American all-purpose, which flour types works through.
The words that are not numbers
Japanese recipes quantify things English recipes leave vague, and leave vague some things English recipes quantify. These are the ones that stop a translation cold.
| Japanese | Romaji | What it asks for |
|---|---|---|
| 少々 | shoushou | A trace, about 0.5 g of salt: what falls from two fingers |
| ひとつまみ | hitotsumami | A pinch, about 1 g: three fingers, so twice a shoushou |
| 適量 | tekiryou | As much as suits, deliberately unquantified |
| すりきり | surikiri | Levelled off flat, the default for a spoon or cup |
| ひたひた | hitahita | Liquid just covering the food, a depth rather than a volume |
Two are worth dwelling on. A shoushou and a hitotsumami are both translated as "a pinch" in English, and one is about twice the other, so a recipe using both is drawing a distinction the translation erases. And surikiri is the default rather than an instruction: a Japanese cup or spoon is understood to be levelled unless a recipe says otherwise, which is the same convention German recipes hold with a bare EL and the opposite of what an unlabelled American cup implies. The fill question in general is on heaped versus level spoons.
A recipe, decoded
Take a plain Japanese sponge, the kind written for a home oven, and read the ingredient list as it would appear. This is what each line means with an American measuring set in your hand.
- 薄力粉 1カップ
- One 200 ml cup of cake flour, 110 g. Not all-purpose, which is stronger and makes the sponge tough.
- 砂糖 1/2カップ
- Half a Japanese cup of johakutou. Weigh it rather than substituting granulated cup for cup, since granulated is heavier for the same volume.
- 牛乳 大さじ2
- Two osaji of milk, 30 ml. Your own tablespoon is correct.
- 塩 少々
- A trace of salt, around half a gram. Not a pinch in the American sense.
- 片栗粉 小さじ1
- One kosaji of potato starch, 5 ml. Cornstarch is a substitute, not a translation.
Three of those five lines would go wrong on a literal reading, and none of the three is a units problem. The cup is a units problem, and it is the easy one: weigh 110 g of cake flour and the hardest line is solved.
What to do in practice
Use your own spoons without adjustment. For anything measured in cups, take the weight from the table above rather than from arithmetic, and if the ingredient is not in it, weigh a Japanese cup of your own by filling a 200 millilitre measure. Check the product name before the quantity, because sugar, starch and breadcrumbs each mean something different in the two languages. And when a recipe says 適量, it is telling you the amount is yours to judge, which is the one instruction no converter can help with.
Questions about Japanese measurements
- How big is a Japanese cup?
- 200 millilitres, against 236.6 for an American one. Rice is the exception: the cup in a rice-cooker box is a go, 180 ml, and the markings inside the bowl count go rather than cups.
- Can I just multiply by 0.85?
- That is the volume ratio and it is the wrong tool. Against the Japanese standard tables it misses by more than a few percent on 10 of our 16 ingredients, in both directions, by as much as 56 percent. Use the measured figure for the ingredient instead.
- Do I need different measuring spoons for a Japanese recipe?
- No. Japanese spoons are 15 and 5 millilitres, the same as metric ones, so a European or American measuring spoon is correct as it stands. The whole risk in a Japanese recipe sits in the cup.
Sources
The Kagawa Nutrition University standard tables, as reproduced by Benricho, and Kyoritsu Foods for the measured Japanese cup weights behind every row above; each ingredient page names which of the two carries which figure. The cup and spoon volumes come from our unit registry. Full citations on the sources page.