Switching from puppy food to adult food

There is no birthday for this. The right moment depends on how big your dog is going to be, and getting it wrong in either direction has real consequences.

When to switch, by size

The logic is straightforward: switch when growth has essentially finished. Reading off our growth reference, dogs reach about 90 percent of adult weight somewhere between roughly 9.5 and 13 months depending on size band.

Not sure which band your dog is in? The size calculator works it out from a weight and an age.

Why switching too early matters

Puppy food is formulated for growth: more energy, more protein, and a controlled calcium and phosphorus profile aimed at building a skeleton.

Moving a still-growing dog onto adult maintenance food takes that away during the period it is most needed. For a large-breed dog still filling out at 12 months, that is a real gap rather than a theoretical one.

Why switching too late matters

The other direction is more common and easier to miss.

Once growth stops, puppy food’s energy density becomes surplus. Combine that with the calorie multiplier having already stepped down at four months, and with an adolescent dog often getting less exercise than a puppy, and weight gain follows quietly.

The switch is a natural checkpoint for recalculating the portion, which is arguably more valuable than the food change itself. Use the feeding calculator at the same time.

How to transition

Over about seven days, mixing increasing proportions:

Slower is fine, and for a dog with a sensitive stomach ten to fourteen days is often better. Faster is where trouble starts: an abrupt change is one of the most common causes of avoidable diarrhoea.

What to watch during the change

• Loose stools for a day or two are common. Persistent diarrhoea, blood, or vomiting are not, and warrant a call to your vet.
• Refusing the new food usually resolves if you slow the transition down rather than giving up and switching back.
• Weight, for a few weeks afterwards. Energy densities differ between foods, so the same scoop is rarely the same calories.

Recalculate the portion, not just the food

This is the step people skip. Adult maintenance and puppy growth use different multipliers, and the new food will have a different energy density.

new cups per day = adult daily calories ÷ kcal per cup of the new food

Both halves of that change at the same time. Carrying the old scoop across to the new bag is how a lean adolescent becomes a heavy two year old.

Large breed dogs specifically

Two points worth holding on to.

Stay on a large breed puppy formula until growth is genuinely done, which for a giant breed can mean approaching two years. The controlled calcium matters for as long as the growth plates are open, as covered in calcium and large breed puppies.

Do not rush to adult food to slow a big puppy down. If growth looks too fast, the answer is portion control on the right food, not the wrong food.

How to know growth has finished

Plot it rather than guess. When the line on a growth chart flattens and stays flat across several weigh-ins, the growing is done. The growth tracker makes that visible.

Height finishes before weight, so a dog that has stopped getting taller may still be filling out for months.

Ask your vet to confirm the timing

This is a genuinely good question for a routine appointment, because your vet can assess body condition, breed, and how the individual dog has grown. A vet who has seen your dog three times over a year has information no calculator does.

The short version

Switch when growth flattens, not on a birthday. Transition over a week. Recalculate the portion at the same time, because the multiplier and the energy density both change.