Running out of dog food always seems to happen on a Sunday evening, and the emergency bag from the corner shop is rarely the right food. This free calculator answers a simple question before it becomes a problem: how many days will this bag last, and when should you order the next one. Enter two numbers and you get a clear plan.
You need the bag weight in kilos, printed on the front of the bag, and the daily food amount in grams. The daily amount is the total your dog eats in a day, including all meals but not counting treats. If you feed by cups, weigh one cup once and multiply by the number of cups per day to get grams.
The maths is simple division: bag grams divided by daily grams gives whole days of food. The calculator rounds down to whole days, because a part day still needs a full meal. It then sets the reorder point three days before the bag runs out, giving delivery time to arrive without panic buying a different food.
Knowing the bag duration also reveals the true monthly cost. A cheap 15-kilo bag that lasts 20 days can cost more per month than a pricier bag that lasts 35 days, once you compare cost per day rather than cost per bag. Divide the bag price by the days it lasts to get the daily feeding cost, and compare foods fairly on that number.
Bag size choice becomes easier too. A single small dog may take two months to finish a large bag, and kibble goes stale once opened, losing smell and taste. For small dogs, smaller bags kept fresh often beat bulk bags that sit open for weeks. For giant dogs, the opposite is true: large bags are finished fast and cost less per kilo.
Storage affects how long food stays good, even if the maths says it lasts. Keep kibble in its original bag inside a sealed container, in a cool dry place away from sunlight. The original bag protects the food better than a bare plastic bin, and it keeps the batch number and best-before date handy if there is ever a recall.
Puppies change the answer fast. A growing puppy eats more every few weeks, so a bag that lasts 30 days today may last only 24 days next month. Recalculate whenever the daily portion changes, and do not buy a huge bag just before a growth spurt if the portion is about to jump. The same applies when a dog starts or stops a weight-loss plan.
Multi-dog homes should calculate per dog, then add the daily totals together. Two dogs eating 300 grams and 500 grams use 800 grams a day between them, so a 12-kilo bag lasts 15 days, not the 24 or 40 days each dog would give alone. Write the shared reorder date on the bag or on the calendar so everyone in the house sees it.
Treats and wet food change the picture as well. If part of the daily diet is wet food, only the kibble portion counts against the bag. For example, a dog eating 200 grams of kibble plus a tin of wet food uses the bag at the 200-gram rate, not the full daily total. Enter only the dry food grams to keep the bag estimate honest.
Set a repeating reminder on the reorder date, not on the run-out date. Three days is enough for most online deliveries, but if your food comes from a specialist shop or a vet practice, allow a full week. A small backup bag of the same food, kept sealed, covers delivery delays without forcing a sudden diet change that can upset the stomach.
This calculator plans shopping, not diets. If your dog needs a prescription food, a weight plan or an allergy diet, the daily grams should come from your vet. Sudden food changes, running out and switching brands overnight, and feeding stale kibble can all cause digestive upset, so plan the bag change with the same care as the portion itself.