How to use the pet food bag duration calculator
- Enter the bag size and choose pounds, kilograms or ounces.
- Choose whether you measure food by the cup or by weight in grams. For cups, enter the cups fed per pet per day and how many cups of this food make a pound. For grams, enter the grams per pet per day.
- Enter the number of pets eating from the bag. Optionally enter the price of the bag and the day you opened it.
- Read how many days the bag lasts, when it runs out and when to reorder, and what the food costs per day and per month.
Formula
Food per day in pounds = cups per pet x pets / cups per pound
Food per day in pounds, by weight = grams per pet x pets / 453.59
Days = bag size in pounds / food per day in pounds
Cost per day = bag price / days
A kilogram is 2.2046 pounds and an ounce is one sixteenth of a pound. The headline shows whole days, and the exact value is in the note.
A 40 pound bag at 3 cups a day
If this food makes 4 cups to the pound, 3 cups a day uses 0.75 pound a day. A 40 pound bag lasts 40 / 0.75 = 53.3 days, so about 53 days. With two pets eating 3 cups each, it lasts about 26.7 days.
Feeding 340 grams a day instead lasts 18,143.7 g / 340 g = 53.4 days. A $55 bag that lasts 53.3 days costs $1.03 a day, which is $30.94 over 30 days. Opened on October 10, the bag runs out around December 2, and the tool suggests reordering a week earlier.
Cups are the weak link
The number of cups in a pound varies a lot between foods, because kibble differs in size and density. The 4 cups to the pound in the example is only an example. Check the feeding guide on the bag or the maker website for your food, or weigh a level cup on a kitchen scale.
A scoop that is not exactly a cup also changes the answer. Weighing the daily portion in grams removes both problems, which is why the tool offers it as an option.
How much to feed
This tool does not decide how much your pet should eat. That depends on size, age, activity and health, and your veterinarian or the food label are the right guide. Treats, wet food and changes in appetite also change how long a bag lasts.
Related tools: the puppy weight calculator and pet age calculator for growth and age, the pet insurance calculator for costs, and the unit price calculator to compare bag sizes.
Assumptions and limits
- The cups per pound, the feeding amount and the bag size are numbers you enter.
- Every pet eats the same amount each day, and the amount stays constant.
- Treats, wet food and waste are not included.
- This tool does not give feeding advice. Ask your veterinarian how much to feed.
Frequently asked questions
How do I calculate how long a bag of dog food will last?
Convert the bag to pounds, work out the pounds eaten per day, and divide. A 40 pound bag at 0.75 pounds a day lasts about 53 days.
How many cups are in a pound of dog food?
It depends on the food, so check the bag or the maker website. The tool asks for it because kibble sizes and densities differ.
How do I account for more than one pet?
Enter the number of pets eating from the bag and the amount per pet. The daily use is multiplied by the number of pets.
Can I use this for cat food?
Yes. Enter the bag size, the amount fed and the cups per pound for that food, and the days work the same way.