How much formula does a baby need? A guide by weight and age
The HSE rule of thumb, a worked table in ml and why the tin is a guide, not a target.
Standing in the kitchen at 3am wondering how much formula to make up is a rite of passage. The good news is there's a genuinely useful rule of thumb, and once you've seen it worked out in real numbers, the whole thing gets a lot less mysterious.
The HSE rule of thumb
For most healthy full-term babies from about a week old up to around 6 months, the guide is roughly 150 ml of formula per kilogram of body weight per day, split across their feeds.
So a 4 kg baby needs somewhere around 600 ml over a full day. Not per feed, per day. Some babies need a bit more, some a bit less, and that's normal. Premature babies and any baby under medical care follow their own plan from the hospital or PHN, so if you've been given specific amounts, use those.
One important caveat: in the first week feeds are tiny and frequent, and the amount builds up day by day. Don't expect the 150 ml/kg figure to apply on day two. It's a guide for once feeding is established, not for a brand new newborn.
Rough daily amount by weight
Here's what the rule of thumb looks like in practice. The last column shows what the daily total looks like if your baby takes 6 feeds in the day, which many do.
| Baby's weight | Rough daily amount | Split over 6 feeds |
|---|---|---|
| 3 kg | about 450 ml a day | 75 ml per feed |
| 4 kg | about 600 ml a day | 100 ml per feed |
| 5 kg | about 750 ml a day | 125 ml per feed |
| 6 kg | about 900 ml a day | 150 ml per feed |
Real babies don't take identical bottles all day, and that's fine. It's the daily total that matters, not any single feed.
How often, and why the tin isn't the boss
Newborns typically feed every 2 to 3 hours, roughly 6 to 8 feeds in 24 hours, spacing out as they grow. But the timing is your baby's to set, not yours. Follow the baby's cues rather than the clock or the tin. The numbers printed on formula tins are averages across many babies, not targets for yours.
Two things never to do:
- Never force a baby to finish a bottle. When they turn away or slow right down, they're done.
- Never add extra scoops or cereal to a bottle. The recipe on the tin is the recipe.
How to know they're getting enough
Forget the maths for a moment. The real signs a baby is getting enough are:
- Steady weight gain, which your PHN tracks at the check-ups
- Around 6 or more wet nappies a day after the first week
- A baby who's generally content between many of their feeds
If those three are in order, the exact ml count matters much less than you'd think at 3am.
Growth spurts and hungry days
Growth spurts, commonly around 2 to 3 weeks, 6 weeks and 3 months, mean hungrier days where the usual amounts suddenly aren't enough. Feed to the cues. It settles again in a few days, and you don't need to change anything permanently.
What changes at 6 months
From around 6 months, once solids start, milk amounts gradually reduce as food takes over some of the work. Formula (or breastmilk) stays the main drink until 12 months though, so the bottles don't disappear, they just shrink.
Making it up safely
One line on preparation, because it matters: make feeds fresh with water of at least 70°C and follow the HSE steps for safe preparation.
And if you're worried about intake, weight or reflux, the PHN and GP are the people to ask. This is a guide, not a prescription.
How we handle it in the app
Lullagram logs every bottle in ml with a quick amount picker, totals the day for you and shows the trend. So "is he taking enough?" becomes a number you can look at, not a worry you carry around. And because both parents see every feed, nobody's doing the mental arithmetic alone at midnight.