Infant Formula Calculator

How much formula does my baby need?

Roughly 150 ml of prepared formula per kg of body weight per day, for the first 6 months. So:

• 3 kg baby: ~450 ml/day, 60-90 ml per feed × 8 feeds.
• 4 kg baby: ~600 ml/day, 75-120 ml per feed × 6-8 feeds.
• 5 kg baby: ~750 ml/day, 120-150 ml per feed × 5-6 feeds.
• 6-7 kg baby: ~900-1050 ml/day (cap ~950 ml).

After 6 months with solids introduced, formula drops gradually to 500-600 ml/day. By 12 months, transition to whole cow’s milk as the main drink.

How do I know my baby is getting enough?

• 6+ wet nappies/day from day 5 onwards.
• Regular poos (formula-fed: every 1-3 days, firmer than breastfed).
• Steady weight gain on their own percentile line.
• Content between feeds, alert when awake.
• Red flags: lethargy, fewer than 6 wet nappies, weight not regained by day 14, persistent fussiness — GP/HV.

How do I prepare formula safely (the 70 °C rule)?

Powdered formula is NOT sterile. WHO 2007 confirmed C. sakazakii (formerly Enterobacter sakazakii) can survive in dry powder and cause severe neonatal meningitis. The 70 °C water is what kills it.

1. Wash hands; sterilise bottle and teat (boiling, steam, or cold-water sterilising).
2. Boil tap water for 1 minute. Let it cool but not below 70 °C (about 10-30 min for a full kettle).
3. Pour the exact amount of water into the sterile bottle first.
4. Add the exact level scoops per the tin instructions. Don’t heap or pack.
5. Shake or swirl to mix.
6. Cool under cold running tap to body temperature (test on inner wrist).
7. Use within 1 hour. Discard leftover. Never reheat or reuse.

How do I do paced bottle feeding?

• Hold bottle horizontally — not tilted steeply down.
• Let baby draw the teat in rather than pushing it in.
• Pause every 30 seconds — gently tip bottle down so milk pauses.
• Watch hunger cues. Stop when baby turns away or closes mouth.
• Don’t push to finish the bottle.
• Use a slow-flow teat appropriate for age (size 1 newborn, size 2 from 3-4 months).
• This mimics breastfeeding pace, reduces overfeeding, supports satiety cues, helps if combination feeding.

Different scenarios — common situations

Scenario 1: 5 kg baby at 4 weeks

Daily target ~750 ml. Split into 6-8 feeds = 90-125 ml each. Watch hunger cues; baby may take less some feeds, more others.

Scenario 2: Baby refusing bottle after exclusively breastfed

Common transition challenge. Try: different teats (Calma, Nuk, Mam, Tommee Tippee Closer to Nature); have someone other than mum offer the bottle initially; warm milk to body temperature; offer when hungry but not desperate; paced positioning. Patience — can take 1-2 weeks.

Scenario 3: 3-month-old with significant reflux

Try anti-reflux formula (Aptamil Anti-Reflux, SMA Staydown). Upright positioning 20-30 min after feeds. Paced feeding. Smaller more frequent volumes. If severe reflux + poor weight gain + feeding aversion, see GP for GORD assessment (NICE NG1).

Scenario 4: Suspected cow’s milk protein allergy

Features: eczema, blood-streaked stools, severe nappy rash, family atopy, persistent reflux despite anti-reflux measures. GP review, possible 2-4 week trial of extensively hydrolysed formula (EHF) like Nutramigen / Aptamil Pepti. Don’t switch to soy formula (60% cross-reactivity).

Scenario 5: Combination feeding — mostly breast but topping up

Common. Each replaced breastfeed reduces supply slightly. Start in the first few weeks with mostly breast to establish supply, then introduce 1-2 formula feeds/day. Use paced bottle feeding so baby doesn’t prefer the easier bottle flow.

Which formula brand should I choose?

Stage 1 First Infant Formula (whey-dominant) is what almost every baby needs. All standard UK / EU first-infant formulas are nutritionally similar — major brands (Aptamil, SMA, Cow & Gate, HiPP, Kendamil, Earth’s Best, Similac, Enfamil) are all fine. Differences are mostly marketing.

• Stage 2 / Hungry Baby / Follow-On — not necessary. NHS / NICE advise sticking with stage 1 until 12 months.
• Specialist formulas (lactose-free, hydrolysed, amino acid) — only if medically indicated.
• Anti-reflux formulas — for troublesome reflux.

What water should I use?

• Cooled boiled tap water (after 1 min rolling boil) is the standard.
• Bottled water if needed — check sodium < 200 mg/L, sulphate low.
• NEVER: distilled water exclusively (no minerals); softened water (too much sodium); well water (untested); repeatedly-boiled water.
• After 6 months, plain tap water is generally fine in countries with safe public supply.

Care guidance — formula feeding well

• Sterilise feeding equipment for the first 12 months (UK NHS), even after solids start.
• Hold and cuddle during feeds — feeding is bonding time too.
• Don’t prop the bottle — risk of choking / ear infections.
• Burp halfway and after feeds.
• One scoop per fluid ounce (most US brands) or per tin instructions — don’t guess.
• Don’t add cereal to bottle without paediatric guidance.
• Vitamin D drops for all formula-fed babies — 8.5-10 mcg/day (UK NHS) for the first year.
• Iron-rich solids from 6 months.
• Transition to cow’s milk from 12 months — full-fat until age 2.

Common myths debunked

• “Hungry baby formula helps baby sleep through” — no consistent evidence. NHS / NICE advise against unless medically guided.
• “Adding cereal to the bottle” — choking risk, doesn’t help sleep. AAP / NHS against.
• “Honey on the dummy / for soreness” — NEVER under 12 months. Infant botulism.
• “Goat milk formula is hypoallergenic” — no. High cross-reactivity with cow milk. Not for CMPA.
• “Microwave a bottle to warm it” — hot spots burn baby’s mouth. Stand in warm water instead.
• “Reheat leftover formula” — bacterial growth risk. Always discard.

Sources

• WHO. Safe Preparation, Storage and Handling of Powdered Infant Formula. 2007.
• NHS Start4Life. How to make up baby formula.
• First Steps Nutrition Trust. Infant milks in the UK: a practical guide for health professionals.
• NICE CG37. Postnatal care.
• AAP. Choosing an infant formula.
• ESPGHAN. Position paper on infant formula.