Ounces to ml Converter (Baby Bottles)
Medically reviewed by Safi Ullah Khan
4 US fl oz = 120 ml. Using US fl oz (29.5735 ml).
Tot is a baby log, not a baby monitor or medical advice. Feeding, sleep and growth ranges vary; always follow your pediatrician's advice. If your baby is unwell, contact your doctor or emergency services.
Medically reviewed by Safi Ullah Khan · Written by Muneeb Rana · Last updated 21 October 2026
Quick answer: To convert ounces to ml, multiply US fluid ounces by 29.57. So 1 oz is about 30 ml, 4 oz is about 118 ml and 8 oz is about 237 ml. UK fluid ounces are slightly smaller at 28.41 ml. Baby bottles usually round to 30 ml per ounce, which is close enough for feeding.
TL;DR
- 1 US fl oz = 29.5735 ml; 1 UK (imperial) fl oz = 28.4131 ml.
- Bottle markings usually round 1 oz to 30 ml.
- For formula, mixing ratios on the tin matter more than rounding.
This ounces to ml converter is built for baby bottles. Type a number in either box and it converts instantly, using US or UK fluid ounces. Below it is a chart of common bottle sizes, so you can match a feeding guide written in ounces to a bottle marked in millilitres.
How to use the ounces to ml
- Pick US or UK fluid ounces (US is the default; most feeding guides, including AAP, use US ounces).
- Type ounces to get millilitres, or millilitres to get ounces.
- Use the chart for common bottle sizes.
- Switch Tot's units to oz or ml so your log matches your bottles.
How the ounces to ml works
ml = oz * 29.5735 # US fluid ounce
ml = oz * 28.4131 # UK (imperial) fluid ounce
oz = ml / 29.5735
| oz | ml (US, exact) | ml (bottle rounding) |
|---|---|---|
| 1 | 29.6 | 30 |
| 2 | 59.1 | 60 |
| 3 | 88.7 | 90 |
| 4 | 118.3 | 120 |
| 5 | 147.9 | 150 |
| 6 | 177.4 | 180 |
| 7 | 207.0 | 210 |
| 8 | 236.6 | 240 |
| 9 | 266.2 | 270 |
| 10 | 295.7 | 300 |
Worked example
A US feeding guide says 4 oz per bottle at 2 months. 4 × 29.57 = 118 ml; on a bottle marked every 30 ml, that's the 120 ml line.
Why US and UK ounces differ
The US fluid ounce is about 4% larger than the UK fluid ounce. At bottle sizes the difference is a few millilitres, but UK formula tins and older UK books sometimes use imperial ounces, so check which one a source means.
Ounces of weight are different
Fluid ounces measure volume. Ounces on a baby scale measure weight (1 oz = 28.35 g). For growth, use the growth percentile calculator, which accepts lb/oz or kg.
Where amounts come from
Use the baby feeding chart or baby feeding calculator for typical amounts by age, and the formula calculator for scoops.
Related: baby feeding chart · baby feeding calculator · formula calculator · growth percentile calculator · baby feeding chart by month · baby feeding tracker
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Sources
- AAP HealthyChildren.org: Amount and Schedule of Baby Formula Feedings: www.healthychildren.org (accessed 21 October 2026)
- CDC: How Much and How Often to Feed Infant Formula: www.cdc.gov (accessed 21 October 2026)
- NHS: Formula milk, common questions: www.nhs.uk (accessed 21 October 2026)
Medical disclaimer:
Tot and this website give general information only. Feeding, sleep and growth ranges vary; always follow your pediatrician's advice. If your baby is unwell, contact your doctor or emergency services.
FAQ
How many ml are in an ounce?
One US fluid ounce is 29.57 ml, usually rounded to 30 ml on baby bottles. One UK fluid ounce is 28.41 ml.
How many ml is 4 oz of formula?
About 118 ml in US ounces, which is the 120 ml line on most bottles.
How many ounces is 120 ml?
About 4 US fluid ounces (4.06 oz).
Is 1 oz exactly 30 ml?
No, it's 29.57 ml, but 30 ml is a common rounding on bottle markings and is fine for feeding.
Which ounces do feeding guides use?
US guides such as the AAP and CDC use US fluid ounces. UK guides such as the NHS mostly use ml.