Every number here comes from NRC & WSAVA methods and is published as open data (CC BY 4.0). See how we check our numbers →
At a typical 3,800 kcal/kg dry food, a 5 lb bag lasts about 31 days for a neutered 5 kg indoor cat (about 281 kcal a day), and a 10 lb bag about 61 days. A smaller 3 kg cat stretches the same 5 lb bag to about 45 days — which is the whole point: the bag size is fixed, your cat’s daily need is not.
For the full portion table by cat weight, jump back to the cat portion size chart.
Two things set this answer: how many calories are in the bag, and how many your cat needs a day. Both are knowable — one from the label, one from your cat’s weight.
Assuming a dry food at 3,800 kcal/kg and a neutered indoor cat of typical activity (1.2 × resting energy). A very inactive indoor cat needs about 1.0× and an active or outdoor cat about 1.4× — so treat these as the middle case.
| Bag size | Total calories | 3 kg cat (191 kcal/d) | 4 kg cat (238 kcal/d) | 5 kg cat (281 kcal/d) |
|---|---|---|---|---|
| 3 lb | 5,171 kcal | 27 days | 22 days | 18 days |
| 5 lb | 8,618 kcal | 45 days | 36 days | 31 days |
| 7 lb | 12,066 kcal | 63 days | 51 days | 43 days |
| 10 lb | 17,237 kcal | 90 days | 72 days | 61 days |
| 16 lb | 27,578 kcal | 144 days | 116 days | 98 days |
Daily needs taken from the same equation used across this site: 70 × kg0.75 for resting energy, × 1.2 for a typical neutered indoor cat. See how many calories a cat needs for the full table, and how many cups are in a bag to get the same bag in scoops.
Three differences matter:
Dry cat food loses its aroma — and cats are notoriously put off by stale food — within about 4–6 weeks of opening. If a bag would take longer than that, buy smaller and more often, even if the price per pound is worse. See shelf life and storage for the same rules (they apply to cat food too).
My cat free-feeds — does this still apply? The arithmetic does, the control does not: with a bowl always full you cannot see how much is going in. Weigh the bowl once a week; if the level drops faster than the table predicts, the amount is higher than you think.
Does a 16 lb bag save money? Per pound yes, but only if your cat finishes it inside the freshness window. For a single small cat, a 10 lb bag is usually the better balance.
My cat is a kitten / senior / pregnant. The multiplier changes, not the equation — see kitten feeding and senior cat nutrition.
Keeping a bag fresh? Airtight cat food containers on Amazon — the smaller the container and the tighter the seal, the longer the food stays appealing.
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Sources: resting energy follows the National Research Council’s Nutrient Requirements of Dogs and Cats (2006); the 1.2× indoor-cat multiplier and the 3,800 kcal/kg typical dry food figure are the same ones used on this site’s cat pages. This page is general information, not veterinary advice.
Cups in a bag → · Calories per cup → · How many calories a cat needs → · Cat portion calculator →