Infant formulas generally come as ready-to-feed liquid, concentrated liquid, and powder. Which type is going to work best for you is likely to depend on how much formula you plan to use, where you plan to use it (ready-to-feed is definitely very convenient when you’re out and about), and how much you want to spend.
Just as pregnancy taught most of you to think in weeks instead of months, bottle-feeding your baby will require you to think in ounces and adopt it as your standard unit of measurement. To prepare you accordingly, we’ll first clarify the basic measures you’ll need for formula success.
1 ounce = 30 cc (cubic centimeters) = 30 mL (milliliters)
8 fluid ounces = 1 cup
32 fluid ounces = 1 quart
Now that you have some frame of reference, we’ll move on to the actual substance of formula preparation.
Powder. The simple concept here is that you add powder to premeasured water and shake a lot. In what we can only assume was an enlightened attempt to eliminate room for mixing errors, most powdered formula is mixed according to the same recipe: 1 scoop of powder to every 2 fluid ounces of water. Powdered formula comes in cans containing enough powder to make anywhere from 90 ounces to more than 200 ounces of prepared formula. It is certainly your most economical choice, and quite frankly works perfectly well for most babies. You can decide whether to mix it up as you go or prepare a full day’s worth at a time and refrigerate it.
Liquid concentrate. This is the “just add water as directed and shake” formula option. Mixing and measuring is again quite straightforward, because all brands of concentrate call for equal amounts of water and concentrate. If you intend to end up with a total of 4 fluid ounces of prepared formula, you’ll need to mix 2 fluid ounces of concentrate with 2 fluid ounces of water. Of course many people choose to mix an entire can of concentrate (13 fluid ounces) with an equal amount of water. The resulting 26 fluid ounces of now-ready-to-feed formula can be covered and put in the refrigerator to be used over the next 48 hours. While some parents find concentrate to be easier, neater, and/or more convenient than powder, it is a convenience for which you will pay more.
Ready-to-feed. This is your no-mixing, no-measuring, no-mess option. Typically sold in 2-,6-or 8-fluid-ounce containers (with anywhere from 4 to 24 to a pack) or 1-quart (32-fluid-ounce) containers/cans, the use of ready-to-feed formula is hopefully self-explanatory—what you see is what you give. While the fairly small “Ready-to-Feed” caption isn’t always prominently displayed on the label, you’d be hard pressed to miss the distinguishing price tag. While buying ready-to-feed formula inevitably costs the most, it leaves almost no room for error (assuming that you don’t mistake it for concentrate and dilute it with water). It also happens to be the easiest way to limit your newborn's exposure to too much flouride. Unopened cans can be conveniently stored at room temperature. Once opened, unused portions can be covered and then refrigerated for up to 48 hours.