The exact amount of energy used on a daily basis for lactation is still a matter of debate.
These calculations should only be used as a guideline, if you find that they are not working for you, you can tweak them until they do. Not everyone is the same, we are all unique and therefore our bodies react differently.
The average lactating woman (who is breastfeeding a newborn) produces between 25 and 32 ounces of milk every 24 hours. Which would mean a 325 – 500 calorie deficit. Calculations are shown below.
Energy used depends on
Is your baby breastfed exclusively? Are any other supplements given?
The age of the child.
These calculations are only accurate if your baby is not supplemented, but sustained by your milk alone. The average metabolic rate would be different if you supplemented with formula or donor breast milk. Therefore it cannot be calculated after 6 months, due to the fact that most babies start solids then.
How our Calorie Calculator Works...
For those mothers who are pumping exclusively, this amount is more easily calculated. You would just take the amount of milk pumped in ounces and times it by 20. This is because there are 20 calories in every ounce of breast milk. For example: if you produce 40 ounces of milk per day, the calories of the milk would be equal to: 800 calories. (40 * 20 = 800)
You would then also need to take into consideration the amount of energy needed to produce that milk. Production efficiency is 80%, therefore, this would be your calculation: 40 * 20 = 800 / 0.8 = 1000. That’s a total of 1000 calories needed extra per day to produce 40 ounces of milk.
But, your metabolism is tweaked during breastfeeding to help you use your calories more efficiently and therefore you need less calories.
Once you have this amount we need to minus the postpartum basal metabolism (you get more out of your calories when breastfeeding). This is the average amount. This differs:
0 – 4 months = 300 calories
4 months = 400 calories
6 months and onwards = 500 calories
So for example: An exclusive pumping mother with a 3 month old baby who expresses a total of 30 ounces per day:
Therefore this mother would add an extra 450 calories to her expended calories for the day when working out how many calories she burns altogether.
Exclusive Breastfeeding mothers
Weigh your baby before and after every feeding over a full
24 hour period. Subtract the before weight from the after feeding weight to
determine how much milk your baby has taken in during each feeding. At the end
of the 24 hours, add up all the amounts to determine the volume taken in during
a 24 hour period. Use the same calculation above. For example: if your new-born
baby drinks a total of 30 ounces daily: 30 * 20 / 0.8 = 750 calories – 300 =
OR a few extra examples:
If your 4 month old baby drinks 30 ounces per day:
30 (ounces of milk) * 20 (calories in milk) / 0.8 (energy to
make milk) – 400 (metabolic increased rate for mother with 4 month old) = 350
(extra calories needed daily)
If your 8 month old baby drinks 32 ounces per day:
32 * 20 / 0.8 – 500 = 300
The amount of calories you consume will also depend on your
Most woman can eat normally while breastfeeding, and might
be a little more peckish than usual, you just need to listen to your body.
To Work out an Average Amount
If you do not want to pump or weigh your baby to work out the exact amount of milk produced, you can use an average amount. Calculate your average amount of milk produced by converting the appropriate amount below from ml to Fluid ounces and use this in the above calculator to calculate your average amount of extra calories needed.