How long should a dog food transition take?

Seven days is the usual plan: a quarter new food for two days, half for two, three quarters for two, then all new. Dogs with sensitive stomachs, and any switch between very different foods (kibble to wet, chicken to fish), do better on ten to fourteen days with the same steps held longer.

What if my dog gets diarrhoea during the switch?

Go back one step and hold it for two or three days before moving on; most upsets settle. Watery diarrhoea for more than a day, vomiting, blood or a dog that stops eating are reasons to stop the switch and call the vet, not to push through.

Can I switch dog food cold turkey?

Only when a vet says so, for instance when the old food is the problem. Otherwise a sudden change is the most common cause of a week of loose stools, because the gut bacteria that break down one food take days to adjust to another.

Why are the grams different for the two foods?

Because the calories per kilogram are: 3,600 against 4,000 in this example. The dog needs 898 kcal either way, so the denser food is 10% less by weight. Read the kcal per kg (or per cup) on both bags and feed by grams, not by the old scoop.

Do I need to change the amount after the switch?

Yes, to the amount for the new food, which is the last column of the tables, and then to the dog: weigh it after four weeks and look at the waist. A food with more calories per kilogram fed with the old scoop is the classic way a dog gains a kilo in a month.

How to switch your dog to a new food: a 7-day plan with the grams

Published 2026-09-17 · 5 min read

A 20 kg (44 lb) neutered dog needs about 898 kcal a day whatever it eats. On a 3,600 kcal/kg food that is 250 g; on a 4,000 kcal/kg food it is 225 g, 10% less in the bowl for the same calories. A switch that keeps the calories steady while the food changes over a week is the one that does not upset the stomach or the waistline, and the table below gives the grams of each food for every day of it.

Dog food calculator

Why the grams change when the food changes

A bag of kibble is between about 3,400 and 4,200 kcal per kilogram depending on the recipe, and the dog needs a fixed number of calories, not a fixed number of grams. Everything below starts from the calories for the dog (the NRC 2006 line for neutered or quiet adults) and works out the grams of each food that add up to them. Two bags, two densities, one calorie target.

The 7-day plan for a 20 kg dog

Old food 3,600 kcal/kg, new food 4,000 kcal/kg, 898 kcal a day throughout. Weigh both on a kitchen scale; the mix can go in the same bowl.

Grams of old and new food per day during a 7-day switch (20 kg dog)
Day	New food share	Old food (g)	New food (g)	Calories
Day 1	25%	187	56	898
Day 2	25%	187	56	898
Day 3	50%	125	112	898
Day 4	50%	125	112	898
Day 5	75%	62	168	898
Day 6	75%	62	168	898
Day 7	100%	0	225	898

For other weights

The same plan scales with the calories: read the grams of each food on its own, and the halfway mix for days 3 and 4. For the quarter and three-quarter days, split the calories a quarter and three quarters the same way, or let the dog food calculator do it with the kcal per kg of your two bags.

Grams per day on each food alone, and the 50/50 day, by dog weight
Dog weight	Calories	All old food (3,600)	All new food (4,000)	Half and half
5 kg (11 lb)	318	88	79	44 + 40
10 kg (22 lb)	534	148	134	74 + 67
20 kg (44 lb)	898	250	225	125 + 112
30 kg (66 lb)	1,218	338	304	169 + 152
40 kg (88 lb)	1,511	420	378	210 + 189

If it goes wrong

Loose stool on day 3 or 5 is common and means the step was a little quick: go back to the previous mix for two days and try again. Refusal of the mix usually means the new food is much less palatable, or the dog has learned that holding out gets the old food back; feed the mix, lift the bowl after twenty minutes, and offer it again at the next meal. Vomiting, blood, or a dog that eats nothing for a day is a vet call, not a patience test.

After the switch

Feed the new amount, not the old scoop, and check in four weeks: ribs easy to feel, a waist from above. If the dog has gained, drop the portion by 10%; if it has lost weight it did not need to lose, add 10%. The tables in how much should I feed my dog give grams for four densities, and how many calories are in a cup of dog food explains why the new bag needs a new cup.

Frequently asked questions

How long should a dog food transition take?: Seven days is the usual plan: a quarter new food for two days, half for two, three quarters for two, then all new. Dogs with sensitive stomachs, and any switch between very different foods (kibble to wet, chicken to fish), do better on ten to fourteen days with the same steps held longer.
What if my dog gets diarrhoea during the switch?: Go back one step and hold it for two or three days before moving on; most upsets settle. Watery diarrhoea for more than a day, vomiting, blood or a dog that stops eating are reasons to stop the switch and call the vet, not to push through.
Can I switch dog food cold turkey?: Only when a vet says so, for instance when the old food is the problem. Otherwise a sudden change is the most common cause of a week of loose stools, because the gut bacteria that break down one food take days to adjust to another.
Why are the grams different for the two foods?: Because the calories per kilogram are: 3,600 against 4,000 in this example. The dog needs 898 kcal either way, so the denser food is 10% less by weight. Read the kcal per kg (or per cup) on both bags and feed by grams, not by the old scoop.
Do I need to change the amount after the switch?: Yes, to the amount for the new food, which is the last column of the tables, and then to the dog: weigh it after four weeks and look at the waist. A food with more calories per kilogram fed with the old scoop is the classic way a dog gains a kilo in a month.

Figures come from the calculators on this site and the published feeding equations (NRC 2006, WSAVA, AAHA). Individual animals vary by up to 30%: adjust by body condition, and ask your vet before changing the diet of a puppy or kitten, a pregnant or nursing animal, or one with an illness.