Quick reference
Breast milk ml to oz conversion chart
Most pumping guides, forums and apps are American and talk in ounces. UK bottles, midwives and health visitors use millilitres. This chart converts between the two so you can make sense of what you read.
Ounces to millilitres
| US fl oz | Millilitres (exact) | Rounded |
|---|---|---|
| 0.5 oz | 14.8ml | 15ml |
| 1 oz | 29.6ml | 30ml |
| 2 oz | 59.1ml | 60ml |
| 3 oz | 88.7ml | 90ml |
| 4 oz | 118.3ml | 120ml |
| 5 oz | 147.9ml | 150ml |
| 6 oz | 177.4ml | 180ml |
| 7 oz | 207.0ml | 210ml |
| 8 oz | 236.6ml | 240ml |
| 25 oz | 739.3ml | 740ml |
| 30 oz | 887.2ml | 890ml |
Millilitres to ounces
| Millilitres | US fl oz |
|---|---|
| 30ml | 1.0 oz |
| 50ml | 1.7 oz |
| 60ml | 2.0 oz |
| 90ml | 3.0 oz |
| 100ml | 3.4 oz |
| 120ml | 4.1 oz |
| 150ml | 5.1 oz |
| 180ml | 6.1 oz |
| 200ml | 6.8 oz |
| 250ml | 8.5 oz |
| 500ml | 16.9 oz |
| 1,000ml (1 litre) | 33.8 oz |
UK ounces and US ounces are different
A US fluid ounce is 29.57ml. A UK (imperial) fluid ounce is 28.41ml. The difference is small for a single bottle, about 1ml per ounce, but it adds up over a day. Almost all online pumping advice uses US ounces, so the charts above use US ounces too. If a UK bottle is marked in ounces, it is most likely imperial ounces, and the ml markings are the more reliable ones to follow.
| Ounces | UK (imperial) | US |
|---|---|---|
| 1 oz | 28.4ml | 29.6ml |
| 4 oz | 113.7ml | 118.3ml |
| 8 oz | 227.3ml | 236.6ml |
Why we track in millilitres
Millilitres are what your bottles, your midwife and NHS guidance use, and they are easier to add up than fractions of ounces. Little Stash logs every session in ml by default, so your totals match the numbers on your bottles.
Common questions
How many ml are in 1 oz of breast milk?
1 US fluid ounce is 29.57ml, usually rounded to 30ml. 1 UK imperial fluid ounce is 28.41ml.
How many ounces is 120ml?
120ml is about 4.1 US fluid ounces, usually rounded to 4 oz.
Is 25 oz of breast milk a day the same as 750ml?
25 US fluid ounces is about 740ml, so it is close to 750ml.
This article is general information, not medical advice. Little Stash is independent and not affiliated with or endorsed by the NHS. If you are worried about your baby's feeding or your supply, speak to your midwife, health visitor or GP, or call the National Breastfeeding Helpline on 0300 100 0212.