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The short answer: for most families of three to six, the 6-quart. Instant rates it for up to six servings, and it’s the size many published Instant Pot recipes are written for. Choose the 8-quart for seven or more, or if you batch-cook beans, rice and grains. The 3-quart suits one or two people, or works as a second pot for sides.
Find your Instant Pot size
How many people do you usually cook for?
Do you often cook big batches of rice, beans or grains?
6 quarts (5.7 litres)
Instant rates the 6-quart for up to six servings, and most published Instant Pot recipes are written for it.
See this size on AmazonInstant's manual caps foods that expand, like rice, beans and grains, at the half line, so batch-cooking them needs a bigger pot.
What Instant says each size is for
| Size | Litres | Instant’s own description | Good for |
|---|---|---|---|
| 3 quarts | 2.8 | “perfect for small households or side dishes” | 1–2 people, or sides |
| 6 quarts | 5.7 | “perfect for up to 6 servings” | 3–6 people |
| 8 quarts | 7.6 | “perfect for up to 8 servings” | 7 or more, or batch cooking |
The two lines inside the pot
The quart figure is the size of the inner pot, not how much food you can pressure-cook in it. Instant’s manuals set two limits:
- The maximum fill line for pressure cooking. Never fill above it.
- The half line, for “foods that expand during cooking such as rice or dried vegetables”, in Instant’s words. The manual also names beans and grains as foods that expand, so they can only fill the pot halfway too.
That second line is the one that changes the size you need. In a 6-quart pot, a batch of beans and their cooking water can come up to about 2.8 litres; in an 8-quart, about 3.8 litres. If you cook beans or grains in bulk for the freezer, that difference is the reason to buy the bigger pot.
Minimum liquid: why bigger isn’t free
A pressure cooker needs enough thin liquid to make steam. Instant’s manual for its Pro models asks for at least 1½ cups (375 ml) in the 6-quart and 2 cups (500 ml) in the 8-quart, unless a recipe says otherwise, and lists too little liquid as a cause of scorching. The figures vary by model, so check your own manual.
So an 8-quart pot doesn’t just cook more: it needs more liquid for the same small meal, and a recipe written for a 6-quart may need adjusting. If you mostly cook one family meal at a time, the 6-quart is the easier pot to live with.
Releasing the pressure
Instant’s manual says to use natural release, letting the pressure drop on its own, after high-starch foods like soups, stews, chilli, pasta and oats, and after foods that expand, like beans and grains. Quick release suits quick-cooking vegetables and delicate seafood. Released steam is hot: keep children well back from the valve.
Is it a slow cooker too?
Most Instant Pot models have a slow-cook setting. If slow cooking is mainly what you want, see what size slow cooker: the sizing works the same way.
Food safety
Instant’s manual says to check meat with a thermometer against USDA’s safe minimum internal temperatures, which our temperature chart sets out with UK guidance alongside. Cool leftovers in shallow containers and refrigerate them within two hours.
Which to buy
Most families
Instant Pot Duo, 6-quart
Good for: families of three to six
- Instant rates it for up to 6 servings
- Instant describes an 18/8 stainless-steel inner pot with a tri-ply base
- Dishwasher-safe lid and inner pot, per Instant
Big families and batch cooks
Instant Pot Duo, 8-quart
Good for: seven or more, or batch-cooking beans and grains
- Instant rates it for up to 8 servings
- Needs more liquid than the 6-quart for small meals
1–2 people
Instant Pot Duo Mini, 3-quart
Good for: one or two people, or a second pot for rice and sides
- Instant: “perfect for small households or side dishes”
- Recipes written for 6 quarts need halving
Useful extra
A spare sealing ring
Good for: anyone who makes yoghurt or puddings as well as savoury food
- Match the ring to your pot’s size
- Many owners keep one ring for savoury food and one for sweet, to keep flavours apart
How we put this together: from the makers’ own published ratings and manuals, and food-safety guidance from USDA and a university extension service, each read on 24 September 2026 and linked where it is used. We have not tested these appliances ourselves and don’t claim to have. This guide tells you what size and type to look for; it is not a ranking.
