Onigiri builder

Making a batch

For packed lunches, picnics or a tray for the freezer. Enter how many onigiri you want, and this works out the rice to cook and the salt, nori and filling you need, using the rice and filling you picked above.

Rice is calculated as 1 g of uncooked rice becoming about 2.2 g of cooked rice (white, brown and similar), or about 1.8 g for sweet rice and sekihan. Japanese recipes measure rice in gō, the cup that comes with a rice cooker: 180 ml, which is about ¾ US cup and about 150 g of rice. The amount of water and how you cook it make a difference too, so cooking a little extra is a good idea.

Which rice to use

Onigiri need rice that sticks together. Japanese short-grain rice is the classic choice; medium-grain rice such as Calrose also works. Long-grain rice like jasmine or basmati does not hold its shape well. Sekihan and sweet rice (glutinous rice) are stickier still and are often used for onigiri on special occasions.

Reading the numbers

• Most of an onigiri's calories come from the rice. 100 g (3.5 oz) of cooked white rice has 156 kcal, so a bigger rice ball has more calories in proportion.
• The salt comes from the salt on your hands and the filling. Plain cooked rice has almost none. Salty fillings such as umeboshi, mentaiko and kombu tsukudani add a lot of salt even in small amounts.
• A full nori wrap (a third of a sheet, about 1 g) adds only about 3 kcal.
• "Salt equivalent" is the sodium in the food expressed as table salt. To convert to sodium, divide by 2.54 (1.0 g of salt equivalent is about 390 mg of sodium).
• Tuna mayo and okaka are estimates made from two foods. Yukari is not listed in the food composition tables, so it is not included.

How to shape an onigiri

1. Wash your hands and spread out a sheet of plastic wrap. Using wrap keeps your hands clean and is more hygienic.
2. Sprinkle salt on the wrap and put the cooked rice on top. Let the rice cool slightly so it is not too hot to handle.
3. Make a small dip in the middle of the rice, put the filling in, and cover it with the rice around it.
4. Wrap it up and shape it gently with your palms without squeezing too hard. For a triangle, bend one hand into a "V" to form the corners.
5. Wrap the nori just before eating for a crisp bite, or ahead of time for a soft, moist wrap.

Food safety when packing onigiri

Onigiri are often eaten hours after they are made. Especially in warm weather, keep these in mind.

• Don't shape them with bare hands. Hands can carry bacteria that cause food poisoning, such as Staphylococcus aureus. Use plastic wrap or disposable gloves.
• Let them cool before wrapping. Wrapping them warm traps condensation, and they spoil faster.
• Pack them with an ice pack in an insulated bag. Keep them out of direct sun and hot cars, and eat them as soon as you can.
• For packed lunches, choose cooked or salty fillings. Umeboshi, salted salmon, kombu tsukudani, okaka and grilled tarako travel well. Keep tuna mayo, mentaiko, takana, ikura and sujiko for onigiri you eat right away.

If anything smells or tastes off, throw it away.

Nori and wrappers

A full sheet of nori (about 21 × 19 cm, or 8 × 7½ in) cut into thirds is just right to wrap a triangle onigiri. You can also buy the same kind of wrapper used for convenience store onigiri, which keeps the nori separate from the rice until you eat it.

Where the numbers come from

Nutrition values are from the Standard Tables of Food Composition in Japan 2020 (Eighth Revised Edition), 2023 supplement, published by Japan's Ministry of Education, Culture, Sports, Science and Technology (MEXT). They are per 100 g of the edible portion, scaled to the amount used in each onigiri.

The weight of each filling (8 g of umeboshi, 15 g of salmon and so on) and the amounts of salt and nori are our own estimates. Real onigiri vary.

To read the nutrition label on a convenience store onigiri, see "How to open a konbini onigiri and read the label."