Before you start: what to decide and prepare
Three decisions before you cook the rice — variety, seasoning, and filling — determine how much prep work you need. Make them now so nothing stalls mid-shaping.
Rice variety
Use Japanese short-grain only: koshihikari, akitakomachi, or domestic Calrose. High amylopectin content is what gives these grains their cohesion under pressure. Medium-grain Calrose works but produces a slightly less sticky result. Long-grain jasmine or basmati will not hold shape — the amylose-to-amylopectin ratio is wrong and the rice falls apart when you press it.
If you are unsure which variety you have or what the label on the bag means, see Japanese Rice Varieties for a full breakdown. The variety context on the Rice hub explains why amylopectin matters structurally.
Seasoning choice
- Plain salted rice (most common): 1 tsp salt dissolved in 1 tbsp water, folded in after cooking. Neutral base that works with any filling.
- Shio koji rice (more complex): 1 tsp shio koji per cup of dry rice, added to the cooking water before the cooker starts. The koji enzymes break down some surface starch during cooking, adding savory depth and a slight sweetness. Use with salmon or umeboshi fillings. See What Is Shio Koji for what it is, and How to Use Shio Koji for proportions and substitutions.
- Sushi-style vinegared rice: rarely used for onigiri — the acidity fights the filling flavors and the rice is harder to shape. Skip this unless you have a specific reason.
Filling: start simple
Choose one filling before you cook. Fillings that need prep time (like cooking salmon) should be ready and cooled before the rice is done. Order of ease:
- Umeboshi — no prep. Pull one medium plum per onigiri, remove the pit. Easiest.
- Salmon flakes — cook first, cool, then shred. 30g per onigiri.
- Tuna mayo — drain canned tuna, mix with Japanese mayo. 30g per onigiri, ready in 2 minutes.
- Okaka — 10g katsuobushi mixed with 1 tsp shoyu. Fastest pantry option after umeboshi.
Rice preparation for onigiri
Onigiri rice uses a slightly lower water ratio than plain gohan — this produces firmer grains that hold shape better when compressed.
Water ratio and cooking
Use 1 part rice to 1.05 parts water by volume — slightly less than the 1:1.1 ratio for plain steamed rice. The reduced water produces firmer, drier grains that compress into a cohesive ball without turning dense or gluey.
Wash the rice until the water runs nearly clear (3–4 rinses), soak 30 minutes, then cook. For the full washing and soaking procedure, see How to Cook Japanese Rice. The only change for onigiri is the water ratio — everything else is the same.
The temperature window for shaping
After cooking, rest the rice covered for 10 minutes, then fold it gently with a rice paddle to release steam. Let it cool to body temperature: 35–40°C. This takes roughly 10–15 minutes uncovered after folding, depending on ambient temperature.
Temperature matters in both directions:
- Too hot (above 55°C): burns your hands, causes excess steam during shaping, and the surface of the ball goes soft and sticky.
- Too cold (below 25°C): the starch has already retrograted — the grains won't bond under pressure and the onigiri falls apart or crumbles.
A reliable test: press the back of your hand against the rice. If you can hold it there comfortably for 3 seconds without pulling away, the temperature is right.
Salting the rice
If using plain salt (not shio koji), dissolve 1 tsp fine salt in 1 tbsp water and fold it into 2 cups of dry rice (cooked weight approximately 600g) after the rest period. Fold, do not stir — you want even distribution without breaking the grains.
Shaping technique
Wet your hands with cold water and rub a pinch of coarse salt between your palms before each onigiri. The moisture prevents sticking; the salt adds surface seasoning and acts as a mild preservative. Re-wet and re-salt between each rice ball.
Triangle shape (sankaku) — standard method
- Portion 180g of cooked rice (roughly one rice-cooker cup worth, cooked) into one palm.
- Press a shallow well into the center with your thumb. Place the filling inside — do not overfill. 20–25g of filling is enough; more and the ball won't close cleanly.
- Fold the rice edges up and over the filling to enclose it completely.
- Cup your dominant hand into a V-shape (index finger and thumb forming one angle of the triangle). Press the top of the ball against this V while your other hand cups the back and bottom.
- Rotate the ball 120 degrees and press again. Rotate and press again. Repeat 4–5 total rotations, applying firm but not crushing pressure. The ball should feel compact — it should not collapse under its own weight — but it should not feel dense or compressed.
Cylinder shape (tawara) — simpler for beginners
- Portion 180g of rice, insert filling as above.
- Roll the rice into a rough cylinder between both palms, pressing the long sides gently.
- Press both flat ends in with your palm to compact the ends neatly.
The tawara shape is easier to maintain under pressure and holds a wrapped strip of nori more cleanly than the triangle. Good default for bento packing where space matters.
Common shaping mistakes
- Overhandling (dense, gummy result): too many pressing rotations or too much force. Stop at 4–5 rotations. The ball should feel firm, not like a compressed hockey puck.
- Underhandling (falls apart): too few rotations or not enough pressure. The rice holds together but crumbles when bitten. Add one or two firm pressing passes.
- Shaping too hot: hands burn, rice surface goes sticky. Cool to 35–40°C before starting.
- Shaping too cold: grains won't bond, ball crumbles. If the rice has gone cold, microwave it loosely covered for 20 seconds and let it settle before trying again.
Fillings — concrete amounts and notes
Umeboshi (pickled plum)
1 medium umeboshi per onigiri, pit removed. The brine from the plum seasons the interior rice as it sits. Most forgiving filling — no prep, no cooking, long shelf life. Choose tart, firm plums rather than the very soft honeyed style, which can make the interior rice wet.
Salmon (sake)
30g cooked flaked salmon per onigiri, plus a pinch of salt. Grill or pan-cook the salmon first, let it cool completely, then break it into coarse flakes. Optionally add 1 tsp toasted sesame seeds. The salmon must be cool before use — warm filling softens the surrounding rice during shaping.
Tuna mayo
30g canned tuna (drained well) mixed with 1 tsp Japanese mayonnaise (Kewpie) per onigiri. The most popular choice for beginners because it binds easily and doesn't leak. Do not substitute western mayonnaise — the egg yolk and rice vinegar balance in Kewpie is what makes this work. If you use too much mayo, the filling becomes wet and weakens the surrounding rice.
Okaka (bonito flakes with soy)
10g katsuobushi mixed with 1 tsp shoyu per onigiri. The soy sauce moistens the flakes just enough to hold them together. This filling uses pantry staples only, takes under 2 minutes, and the glutamates in the katsuobushi pair well with the plain rice. For more on the umami structure of katsuobushi and kombu, see What Is Kombu.
Nori wrapping
Standard nori sheets measure 20×19cm. How you wrap depends on whether you are eating now or packing for later.
Full wrap — traditional, eat immediately
Lay one full sheet of nori flat. Place the shaped onigiri at one edge and fold the nori around the base and sides, pressing it to the rice. Tuck the edges under the base. Eat within 15–20 minutes — the nori softens as it absorbs moisture from the rice, which many people prefer, but it becomes fully limp after 30 minutes.
Half-strip — bento style, less soggy
Cut one sheet into a strip approximately 3×19cm. Wrap it around the base of the onigiri only, leaving the top exposed. This gives you a grip point without covering the full surface, so the nori stays firmer longer. Standard for bento boxes where the onigiri will sit for 1–3 hours before eating.
Separate nori — maximum crispness for packing
Pack the onigiri and a separate piece of nori in the same container. Wrap just before eating. Nori stays crisp for up to 4 hours this way. The "konbini" style onigiri with the plastic separator that keeps nori dry until you peel and assemble uses this same principle.
Storage
Room temperature
Onigiri keep at room temperature for 2–3 hours in cool conditions (below 20°C). In summer, reduce to 1–2 hours. Nori-wrapped onigiri degrade faster because the nori holds moisture against the rice.
Refrigerator
Refrigerate in an airtight container for up to 24 hours. The rice will harden in the cold — starch retrogradation happens rapidly below 15°C. Reheat before eating: microwave 30–40 seconds covered with a damp paper towel. The steam from the towel re-gelatinizes the starch and restores the original texture. Without the towel, the surface dries out and the interior stays hard.
Freezer
Freeze onigiri without nori only. Wrap each rice ball individually in plastic wrap, then seal in a freezer bag. Freeze up to 1 month. To reheat from frozen: remove plastic, wrap in a damp paper towel, microwave 2–3 minutes at 600W. Add nori after reheating. Freezing nori-wrapped onigiri makes the nori rubbery and impossible to crisp up again.
Where to go next
For rice cooking fundamentals — washing, soaking, and the base 1:1.1 ratio — see How to Cook Japanese Rice. For variety differences and which koshihikari brands are available outside Japan, see Japanese Rice Varieties. For the sushi rice comparison (what changes and why), see Sushi Rice vs Short-Grain Rice. For what to do with leftover onigiri rice, see the Leftover Rice Guide. The full rice context — amylopectin, brand comparisons, variety guide — is at the Rice hub.