270ml vs 120ml Baby Bottle Sets: Which Size to Start With
By BIBS | Published: 2026-11-01
Category: Buying Guides
A practical baby bottle size guide for choosing between 120ml and 270ml sets, with clear decision rules for newborn feeds, growing appetites, and material trade-offs.
Quick answer
Start with a 120ml glass baby bottle set for the newborn stage, then add a 270ml BPA-free PP bottle set once feeds regularly pass the small bottle’s comfortable fill. If you want one set to cover both stages, buy the 270ml set and treat the 120ml as your early-days top-up.
Why the 120ml size earns its place first
Newborn stomachs are small, and early feeds are frequent. A 120ml bottle keeps the portion visually close to what you are actually serving, which makes it easier to notice when your baby is slowing down rather than finishing a large bottle out of habit. That is the practical reason a newborn bottle size tends to sit at the smaller end.
The trade-off is longevity. A 120ml set will feel too small sooner than you expect once feed volumes climb, so plan for it as a stage-one purchase rather than your only bottle.
When 270ml becomes the better default
The 270ml size suits babies who take larger, less frequent feeds and parents who prefer to mix one bottle to cover a full feed without topping up. It is also the more forgiving choice if you are unsure how much milk per feed your baby will take in the coming weeks.
The downside is that a large bottle can encourage over-pouring for a small newborn. If you start with 270ml, measure the amount you intend to serve rather than filling to the top.
Material changes the size decision
The 120ml set in this comparison is borosilicate glass, which is temperature- and thermal shock-resistant and does not emit microplastics into the milk. That makes it a natural fit for the newborn stage, when you are warming and cleaning bottles constantly.
The 270ml set is BPA-free polypropylene, which is lighter for older babies who want to hold or carry their bottle. Neither material is automatically better; the size you need at each stage should drive the choice.
Decision rules for choosing your first bottle size
- If your baby is newborn or taking small, frequent feeds: Choose the 120ml glass baby bottle set as your primary bottle. It matches early feed volumes and the glass construction suits repeated warming and washing. Buy at least two so one is always clean and ready.
- If feeds are already larger or you want one set to last: Choose the 270ml BPA-free PP bottle set. Its larger capacity covers bigger feeds and the polypropylene body is lighter for older babies to hold. Measure each feed rather than filling the bottle to the top.
- If you are unsure and want a two-stage plan: Start with the 120ml glass set for the first weeks, then add the 270ml PP set when your baby consistently finishes the smaller bottle. Reassess the flow option when you move up a size.
Product facts
- Baby BPA-Free PP Bottle Set 270ml Latex - Blush: 270ml BPA-free polypropylene bottle with a round natural rubber latex nipple, available in Medium Flow. The larger capacity and medium-flow nipple suit babies taking bigger feeds, but the flow option is fixed, so check it matches your baby’s pace before relying on this as a newborn bottle.
Baby BPA-Free PP Bottle Set 270ml Latex - Blush - Baby Glass Bottle Set 120ml Latex - Ivory: 120ml borosilicate glass bottle with a round natural rubber latex nipple. The small glass bottle is a sensible newborn size and avoids microplastics in the milk, but glass is heavier to hold once your baby starts self-feeding.
Baby Glass Bottle Set 120ml Latex - Ivory
Who each size suits
Best for
- Parents preparing for a newborn who want a small, glass bottle for early feeds
- Caregivers who prefer a lightweight, larger bottle for babies taking bigger feeds
Not for
- Parents who want a single bottle size to cover every stage from day one
- Babies who need a specific flow rate not offered in the chosen set
