What this page will not do
It will not tell you how much to feed. That figure is an input here, and it comes from your veterinarian or from the feeding guidance printed on the bag you actually buy. There is no body weight field on this page and there will not be one, because turning a weight into a portion is a judgement about an animal rather than a calculation, and it depends on the specific food, the individual dog and things only a veterinarian can assess.
What this page does is everything downstream of that number: how long a bag lasts, what a day of feeding costs, when the next bag has to be ordered so you do not run out, and how big a sealed container needs to be to hold one. That is ordinary household arithmetic and it is genuinely tedious to do by hand, mostly because it involves converting between cups, grams, pounds and litres in the same sum.
The cup problem
A cup is a volume and a bag is a weight, so any calculation that starts from cups needs a bulk density to bridge them. Kibble runs roughly 90 to 130 grams per cup depending on the piece size and shape, which is a spread of about 40 percent, and that spread lands directly on your days-per-bag figure. Small dense pieces pack more into the same cup than large airy ones.
Many bags state the grams per cup somewhere on the packaging, and if yours does, use it. If it does not, the reliable move is to weigh one level cup of the food on a kitchen scale once and put that number in. It takes a minute and it makes every figure on this page accurate rather than approximate. Feeding by weight rather than by cup removes the problem entirely, which is why the portion field accepts grams and ounces.
The reorder point, and why it is in days
The threshold is the lead time plus a safety margin, both in days, compared against how many days of food are actually in the house. Expressing it in days rather than in bags is what makes it useful, because a bag is a different amount of time for every household.
| Situation | Lead time | Sensible margin | Why |
|---|---|---|---|
| Shop five minutes away, always stocked | 1 day | 2 to 3 days | Only covers the evening you cannot get out |
| Ordered online, standard delivery | 3 to 5 days | 5 to 7 days | Delivery slips, and a weekend can absorb two of those days |
| Ordered from a specialist or a distance | 7 to 14 days | 10 to 14 days | Backorders happen and substitution is the thing you are trying to avoid |
| Subscription on a fixed cycle | Cycle length | Half a cycle | The failure mode is the cycle drifting out of step with consumption |
The margin exists specifically so that running low does not force an unplanned change of food. That is the actual cost of poor timing, and it is not a money cost.
Containers, and keeping the bag
The container figure is the bulk volume of one bag plus twenty percent, which covers the fact that a container has to close over the food and that a scoop has to go in. A 30 pound bag at typical kibble density is around 31 quarts, so a 37 quart container is the smallest that works and a 40 quart one is comfortable. This is the number people get wrong most often, because they reason from the weight on the bag and containers are sold by volume.The habit worth building is to keep the food inside its own bag and put the bag in the container, rather than tipping the kibble in loose. The bag carries the batch code and the best-before date, which are the two things you need if there is ever a recall, and they are gone the moment the bag goes in the bin. It also means the container itself only ever touches the outside of a bag, so the residue that builds up in a container used loose does not build up at all.
If you are pricing bag sizes against each other, the bulk buy calculator handles the case where the bigger bag is cheaper per pound but goes stale before you finish it. The pet cost calculator puts the annual food figure next to everything else, and if the storage is competing for floor space, the storage unit size calculator works in the same volumes.
Questions people ask
How long does a bag of dog food last?
Divide the bag weight by the daily portion, once both are in the same units, which is exactly what this page does. A 30 pound bag fed at three cups a day, with kibble at 110 grams per cup, lasts about 41 days. Change the density to 130 grams per cup and the same bag lasts 35 days. That is why the grams-per-cup figure matters more than it looks: it moves the answer by a fifth. Weigh one cup of your actual food once and the number stops being an estimate.
How much should I feed my dog?
This page does not answer that and no calculator should. The portion is an input here precisely because it is a judgement about a specific animal eating a specific food, and it depends on things a web page cannot see. Get the figure from your veterinarian, or from the feeding guidance on the bag you are actually buying, and put that number in. Everything on this page is arithmetic downstream of it and none of it changes what the right portion is.
What size airtight container do I need for a bag of dog food?
Work in volume rather than in the weight printed on the bag, because containers are sold in quarts or litres and food is sold in pounds. At typical kibble density a 30 pound bag is around 31 quarts, a 40 pound bag around 41, and a 15 pound bag around 15. Add about twenty percent so the lid closes over the food and a scoop fits, which is what the figure on this page does. If you buy two bags at a time, two containers beat one big one because the older bag stays identifiable.
Should I pour the food into the container or leave it in the bag?
Leave it in the bag and put the bag in the container. The bag carries the batch code and the best-before date, and both of those are what you need if the food is ever subject to a recall, which is not a rare enough event to plan around losing the information. Bags are also generally built to keep the fats in the food from picking up air, which a general-purpose plastic bin is not. The container is doing the pest and moisture job on the outside of the bag, which is the job it is good at.
Is the bigger bag always cheaper?
Per pound, usually. In practice, only if you finish it in reasonable time. A bag that lasts four months has been open for most of that, and manufacturers date bags on the assumption they are unopened. Weigh the saving against how long the days-per-bag figure says it will be open, and if the number is high, the smaller bag more often is frequently the better buy even at a worse unit price. The bulk buy calculator does that comparison directly if you want to put numbers on it.