Puppy feeding and growth
How much should an 18 month old puppy eat?
Last updated 23 September 2026 · How we write and check this
Short answer
By eighteen months, the vast majority of dogs, including large breeds, have reached adult size and should be eating an adult amount of adult food. Giant breeds are the main exception and can still be finishing their growth right up to around 24 months, so check weight trends before assuming this dog is fully grown.
The end of the road for most breeds
Small and medium breeds reached adult size long before this, and large breeds typically finish somewhere between 12 and 18 months, which makes eighteen months a reasonable point to confirm every non giant breed is on an appropriate adult diet with portions matched to its actual adult weight rather than an outdated puppy chart.
Giant breeds: often not quite there
A giant breed such as one that will exceed 50 kg (110 lb) as an adult can still be gaining weight and filling out at eighteen months, with growth sometimes continuing to around two years old. If monthly weigh ins still show a clear upward trend, keep this dog on its growth appropriate formula a little longer.
Recalculating portions for a now adult dog
Once growth has genuinely stopped, recalculate the daily food amount from scratch using the adult dog's actual weight, activity level, and the adult food's calorie content, rather than simply continuing whatever amount the dog happened to be eating as a puppy.
Key takeaways
- Most dogs, including large breeds, have reached adult size by eighteen months.
- Giant breeds can still be growing at this age, sometimes until around two years old.
- Confirm a flat weight trend over several weeks before finalising the switch to adult food.
- Recalculate portions from the dog's actual adult weight rather than its old puppy amount.