We are currently using medela bottles and the bottles only go to 5oz. Abby is starting to eat 4-5 oz ( depending on the time of day) so I figure we'd just move up to bigger bottles now. I have the shells and a bunch of boxes of playtex drop ins from my baby shower and I'm going to start using those.
I wanted to make sure the measurements on the bottles were correct so I poured 4oz in from the medela bottles and it showed up as over 6oz in the playtex bottle! The drop ins and the bottles say they are 8oz.
My question: Would you measure out 6oz of water ( in the drop in) but only put 2 scoops of powder ( for "4 oz"), or measure out the 4oz in another bottle and pour it in ( like I've been doing)?
Here's a pic of the same amount of water in each bottle:

Maybe I'm just sleep deprived, but this seems so confusing.
Re: playtex drop ins question!
I've found the drop in liners don't always stretch out to accurate. I'd pre measure the water then pour in.
There are two types of drop ins for Playtex. One is the 8 oz and the other is the 10 oz expandable drop ins. If you look at the bottle one side has the 8 oz measurements and the other has the 10 oz measurements. I think you are using an 8 oz liner and reading the 10 oz measurement on the bottle. Hope this makes sense. Regardless I would still use the Medela bottles to measure the water.
This.
I premix formula in a seperate container and then pour into the bottles (i use a shaker meant for protein shakes that has ounce measurements on the side and mix a full can of concentrate at a time). Platex bottles just aren't super accurate because the "puff out" and some expand more than others. But make sure you are looking at the right side of the bottle, because there are two scales on it.
I JUST realised that there are 8 and 10oz markers on the bottle. I was using the 8oz side, and I'm using 8ox drop ins. I guess I'll pre mix and then pour it into the drop in.
Thanks so much