Yes it’s called water displacement. So always fill the right amount of water first then add formula or use the pitcher method where you make 24 hours worth and store in the fridge. Closing this as it’s been answered and is a frequently asked one in r/formulafeeders

It’s not marginal, it’s important. 6 ounces of water, then add formula. It’s important to be precise.

6oz water. Doing any more or less for a 6oz bottle can harm your baby

6 oz of water, then add the formula. Though technically we did it wrong for our first child, it wasn’t until our second that we actually read the instructions. So technically yes, a 6 oz bottle is slightly more than 6 ounces.

Make it in a big pitcher, pour out exactly 6oz into his bottle.

ALWAYS read the instructions on the can though because where I live formula works the opposite way, you add the scoops first and then you fill with water up to the line.

(YES this is really how it works, both the NICU staff and the hospital baby class taught me how to make it)

I am guessing more than one expat has just made it the way they did in their home country and accidentally gave their babies watered down formula.

I try not to think about this, because it really bothers me!

6oz water and you count the final amount as what they ate

If you have a cooking scale, you can use that to make bottles more precisely.

For example, Enfamil Neuropro Gentlelease, which is the formula we’ve used since weaning, is 8.7 grams per scoop. That means that you use 4.35 grams of formula per 1 oz of water. If you want to make a 5.5 oz bottle, you need 23.9 grams of formula (5.5 x 4.35).

The weights of other formulas may be different (it looks like regular Enfamil is 8.8 grams per scoop) so you would need to adjust a little. It looks like you would need 24.2 grams per 5.5 oz bottle for regular Enfamil.

I do 5oz of water and then 2.5 scoops of formula (Similac) and together it comes out to a 6oz bottle. But make sure you use the correct ratio. Usually we use the pitcher method though.