An opened can of powdered formula stays safe to use for one month. Once you open the lid, write the date on top and plan to use or discard the contents within 30 days, regardless of how much powder is left. For most newborns eating formula exclusively, a standard 12.5-ounce can of powder will last roughly 3 to 5 days, so spoilage from sitting too long is rarely an issue in practice.
But “how long does a can last” has a few layers. There’s the shelf life of the opened container, how quickly your baby will actually go through it, and the tighter time limits that apply once you mix a bottle. Here’s how all of that breaks down.
Shelf Life of an Opened Can
Powdered formula should be used within one month of opening. Store it with the lid tightly sealed in a cool, dry place. The pantry or a kitchen counter away from the stove works well. Don’t refrigerate the powder, because moisture inside the fridge can cause clumping and encourage bacterial growth.
Unopened cans last until the expiration date printed on the bottom. Never use formula past that date, even if the can has never been opened, because the nutrients degrade over time and the manufacturer can no longer guarantee safety.
Liquid concentrate and ready-to-feed formulas follow different rules. Once you open one of those containers, refrigerate it immediately and use it within 48 hours (check the label, since some brands specify 24 hours). These products spoil faster than powder because they already contain water.
How Fast a Newborn Goes Through a Can
In the first few days of life, most babies take just 1 to 2 ounces per feeding. They eat frequently, though, typically 8 to 12 times in 24 hours. That puts a brand-new baby at roughly 15 to 20 ounces of prepared formula per day.
A standard 12.5-ounce can of powdered formula makes approximately 90 fluid ounces when mixed. At 15 to 20 ounces a day, a newborn in the first week will go through that can in about 4 to 6 days. By the end of the first month, many babies are drinking closer to 24 to 32 ounces daily, which means you’ll burn through a can in roughly 3 days. Over the course of a full month, expect to use somewhere around 8 to 10 standard cans if your baby is exclusively formula-fed.
Can sizes vary by brand. Some come in larger 20- or 30-ounce containers, which obviously last proportionally longer. The math is straightforward: check the label for how many fluid ounces the can yields, then divide by your baby’s daily intake.
Time Limits for a Prepared Bottle
Once you’ve mixed powder with water, the clock starts ticking on a much shorter timeline. Prepared formula that hasn’t been offered to the baby yet is good for 2 hours at room temperature. If you want to make bottles ahead of time, refrigerate them right away and use them within 24 hours.
The moment your baby starts drinking from the bottle, the window shrinks to just 1 hour. Saliva introduces bacteria into the formula, and those bacteria multiply quickly in a warm, nutrient-rich liquid. After an hour, toss whatever is left, even if your baby only drank half. This is one of the firmest safety rules in formula feeding and applies to every type of formula.
Reducing Waste
Newborns are unpredictable eaters, and pouring out half-finished bottles feels wasteful. A few practical strategies help:
- Start with smaller bottles. Prepare 1 to 2 ounces at a time for a newborn. You can always mix more if your baby is still hungry, but you can’t save a bottle that’s been sipped from.
- Batch-prep and refrigerate. Mix a day’s worth of formula in a clean pitcher, store it in the fridge, and pour individual bottles as needed. The pitcher stays safe for 24 hours since no saliva has touched it.
- Track feeding patterns. After a week or two, you’ll notice your baby settles into a rough pattern. If they reliably take 3 ounces at a time, prepare 3 ounces instead of 4.
Signs a Can Has Gone Bad
Powdered formula that has absorbed moisture may look clumpy, discolored, or have an off smell. If the powder doesn’t dissolve smoothly when mixed or if the prepared bottle smells sour or unusual, discard it. A can with a dent, rust, or a bulging lid should also be thrown away, even if it’s within date. These are signs that the seal may have been compromised.
If your baby refuses a bottle they’d normally accept, that can also be a clue the formula has turned. Babies are surprisingly sensitive to taste changes, and sudden rejection is worth paying attention to.