Meddor
Switching foods means mixing the old and the new over 7 days, or 14 with the calculator. Enter the portion printed on the new food’s bag, or your dog’s or cat’s weight if you don’t have the bag: the calculator works out how many grams of each food go in the bowl, every day.
Why switch foods gradually
Switching foods too fast can cause diarrhoea or vomiting. So the vets at the University of Missouri’s Veterinary Health Center recommend a gradual transition, mixing the old and the new food. The total amount stays the same: only the proportions change.
According to WSAVA, some animals cope with an abrupt change, but others have fewer digestive problems when the food changes over 7 to 10 days.
Dog food transition chart (7 or 14 days)
The 7-day plan is the one the University of Missouri vets give, and the one the calculator follows:
| Days | Old food | New food |
|---|---|---|
| 1 and 2 | 75% | 25% |
| 3 and 4 | 50% | 50% |
| 5 and 6 | 25% | 75% |
| 7 | 0% | 100% |
The calculator also offers a 14-day plan, more gradual: the new food starts at 15% instead of 25%. WSAVA mentions 7 to 10 days; choose the length with your vet if your pet has a sensitive stomach.
What about the portion itself?
The calculator starts from the portion printed on the new food’s bag, or, without the bag, estimates it from your pet’s weight. The full calculation, its sources and its limits are on our page how much to feed a dog or cat.
Frequently asked questions
Can I switch foods overnight?
Better not, unless your vet asks you to, for a prescription diet for example: a switch that’s too fast can cause diarrhoea or vomiting.
Loose stools during the transition: what should I do?
Talk to your vet: they’ll tell you whether to go more slowly. Call them straight away if there’s vomiting, blood, or your pet seems listless.
My cat won’t eat the new food
Many cats are wary of anything unfamiliar. The University of Missouri vets suggest serving the new food in a separate bowl, next to the old one, rather than mixed. If your cat stops eating, talk to your vet quickly.
What about switching from wet food to dry food?
Grams don’t carry over from one type to the other: wet food contains much more water. Run the calculator twice, once with each pack, and apply the plan’s percentages to each of the two portions.
Should the amount change during the transition?
Not between two foods of the same type: each day, the grams of old and new food add up to the daily portion. The proportions change, not the size of the meal.
Sources
- University of Missouri, Veterinary Health Center, “Nutrition: frequently asked questions”: the 7-day plan, wary cats, two bowls.
- WSAVA, “Nutritional Assessment Guidelines”, 2011: a 7 to 10-day transition.
- The portion calculation: see the sources on our portion calculator page (Merck Veterinary Manual, FEDIAF).