Use the free Cat Food Bag Calculator below, right in your browser. No sign-up, no software to install, and nothing is sent to a server.
Running out of cat food at night is a small crisis every owner knows. The Cat Food Bag Calculator answers a simple question before it happens: given the bag size and the daily portion, how many days will this bag last, and when should you reorder?
The maths is one division. A 2 kilo bag holds 2000 grams, so at 60 grams per day it lasts 33 days. At 50 grams per day the same bag lasts 40 days. Small changes in the daily portion change the answer by days, which is why weighing food matters for this estimate as well as for weight control.
To use the tool, enter the bag weight in kilos, the daily food in grams, and how many cats share the bag. The tool gives the days the bag lasts and a reorder day three days earlier, so a delivery has time to arrive. If you buy in a shop, the reorder day is simply your shopping reminder.
Try the default example. A 2 kilo bag at 60 grams per day for one cat lasts 33 days, with a reorder reminder at day 30. For two cats at 60 grams each, the same bag lasts only 16 days, because the daily total doubles. Multi-cat homes are often surprised by this, and the tool makes the doubling visible.
Cost per day is the useful second number. Divide the bag price by the days it lasts to compare bags fairly. A big bag that looks expensive may cost less per day than a small bag on offer, while a small bag that goes stale before it ends costs more than the label says, because the last portion is wasted.
Storage affects how big a bag you should buy. Dry food stays fresh for about 6 weeks after opening if kept sealed, cool, and dry, in its original bag inside a sealed container. A bag that lasts 90 days for one cat may go stale near the end, so for one small cat a 2 kilo bag often beats a 10 kilo bag on freshness.
Treats and wet food change the dry food days. If your cat also eats wet food, the dry portion per day is smaller, and the bag lasts longer than the full portion maths suggests. Enter the dry grams actually served per day, not the total food target, and the answer stays honest.
Set the reorder reminder the day you open a bag, not the day it runs out. Three days covers most deliveries, but if your food comes from a specialist shop or a subscription, use a week instead. A buffer of one extra day of food in a sealed jar covers late deliveries without panic.
Keep a note of the open date on the bag with a marker pen. When the next bag opens sooner or later than the tool predicted, check the daily portion first: a scoop that drifted heavier will shorten every bag, and a new food with different density changes the grams per day even at the same calories.
Use the calculator each time you change food, portion, or cat count, and the surprise runs out for good. A bag that lasts a known number of days turns shopping into a routine, keeps the cat fed without emergency shop trips, and makes the true monthly food cost easy to see.
Subscriptions and bulk orders work best when they follow the calculator, not a fixed monthly guess. Set the delivery gap to the bag days minus a few days of buffer, and review it whenever the portion or the cat count changes. A subscription that arrives every 30 days for a bag that lasts 40 days will slowly build a stockpile, while one set for a bag that lasts 25 days will run out before the next box arrives. Match the gap to the maths, and the food cupboard stays steady without emergency orders.
Versión en español: Duración del saco de pienso para gatos – Días según ración