The “One Ounce Per Hour” Rule

One of the frequently asked questions of breastfeeding is “How much milk should I leave my baby while we are separated?”

The answers that I’ve seen vary. The answer that I subscribe to is “The One Ounce Per Hour Rule”.  (Which could be better described as the 1-1.25oz/hour rule).

The one ounce per hour rule is based on the average daily requirements of a breastfed infant who will take in 25oz/day of milk. (This does not vary much between one and six months). While amounts might be more or less during exclusive pumping / bottle feeding, the “One Ounce Per Hour” rule is considered the standard for shorter periods of mother and infant separation.

This method is the “breastfeeding friendly” method that is most likely to lead to longer term breastfeeding success. Other methods that allow on-demand feeding from bottles or that follow amount guidelines for formula fed babies often lead to supply decrease and early weaning or supplementation of non-human milk.

I’ve heard a lot of moms say that they are anxious about the one-ounce-per-hour rule of feeding a breastfed infant while separated from mom. I understand it. I was anxious as a new mom, too, and wanted to leave MORE than my baby needed because it hurt to leave him and I wanted to make sure he would be happy and satisfied while I was away.

The thing is.. It’s not starving your baby and it’s not letting your baby go hungry. It’s something your baby is already used to. The supply in your breasts is not static. It goes up and down across the day. Your baby is already used to this.

Your baby eats the same amount each day between one month and when solids are introduced. (A bit more during growth spurts- but this should happen at mom’s breast, since her supply has to scale.) This amount for breastfed babies averages out to 25oz/day with some babies eating as little as 19oz/day. Your supply is not static across the day, it increases and decreases across the day, so baby learns to nurse more during high supply hours, and less during low supply hours (which are typically in the evening)

What the one ounce per hour rule does is it encourages baby to view the bottle feeds as “low supply”, and mom-feeds as “high supply” and baby nurses more with mom and less with the bottle. Baby’s needs are met, not exceeded. More than one ounce per hour means baby finds bottle = high supply, breast = low supply, and starts fussing for more bottle, less mom. This means mom is stuck pumping HUGE amounts of milk.

This causes problems because the pump is ineffective. It’s like trying to siphon water out of a well with a drinking straw. It’s tedious, it’s boring, it’s a pain in the butt. Mom’s breasts let down easily to an eager baby, and noooot so well to a pump. 1-2oz per pumping session is actually EXCELLENT output. If baby is downing 2oz/hour or more than one ounce/hour? Mom would have to pump constantly at work to make up for it.

Better to convince baby that the bottle has a rotten supply and that it’s easier to gorge off mom. Easier on mom, easy enough on baby, and baby’s needs are more than met with the ounce per hour.

Sources: Average Intake of Breastmilk (Kellymom)

*** Important caveat: As with all “rules” there are exceptions. If mom and baby are routinely separated from each other during ALL of the highest supply hours of mom’s day and are only together briefly, the one ounce per hour rule might not work and baby may need more frequent feedings during separation. View the rule as a guideline and as a possible warning sign that your caregiver is overfeeding the baby or giving bottles that are too large/too frequent. It may not be the amount that is a problem but the bottle size. Maybe baby will do better with more frequent 2oz bottles. Maybe your pumping sessions need to be longer or more frequent in order to get milk of the right composition for what baby needs while separated. Never follow ANY rule that doesn’t work for your child.

  10 comments for “The “One Ounce Per Hour” Rule

  1. January 6, 2012 at 2:14 am

    The only thing I would add to this is that if you are delaying solids significantly past 6 months (which is fine) you may find that baby’s milk needs increase around 6 months until such time as solids are added. If solids are added around 6 months, the milk needs should stay stable while solids add to the total intake.

  2. amber garrison
    May 11, 2012 at 9:31 pm

    Great info! My lo is 8 months now but somehow in all the info I read I never came across this method :-(. Will definately keep in mind for the next one.

  3. Bethany B.
    June 24, 2013 at 4:50 pm

    Thank you for this article! If I had had this sort of information when my daughter was an infant and I had to go back to work, I might not have panicked nearly so much as I did the first year when she was primarily on breastmilk.

    I had access to great lactation nurses, but they didn’t talk at all about reverse cycling, or much about what normal pumping output was other than if you’re with your baby all day, you won’t get much; though if I were with my baby all day, I wouldn’t need to pump much. They also fed into the fallacy that if you’re at work, you should be getting tons out because you won’t be with your baby and it will build up to baby levels and just come out easy peasy lemon squeezy. So not true.

    It took several books on lactation and articles like this to get me to not worry incessantly about it. Given that breastfeeding is often stated as a supply/demand situation, you’d think this would be more talked about.

  4. Sharmaine
    January 14, 2014 at 10:08 pm

    thank you for this :)

  5. Mary
    March 7, 2014 at 2:54 am

    Hello! I would like to say that this is a very insightful article. It is currently my guide to feeding my child while I’m at work. :) My only question is, do we need to feed our LOs more during their growth spurt? As we all know, they tend to feed more during this period. :) If so, how much or how often should we feed them? Looking forward to your reply. Thank you!

    • sarah
      March 7, 2014 at 10:30 am

      All “rules” have to be modified to fit the child and the mother. The goal is to have a child that is not hungry (but not necessarily “satisfied” or “full”) and a mother that is able to pump what her child eats during the day. Many babies will be fine with continuing the 1oz/hour rule and will nurse more often when with mom to get what they need for their growth spurt. Other babies may need more frequent feeds or may temporarily go up to 4oz bottles from the 3oz bottles. (I would choose more frequent feeds rather than larger ones, if possible.)

  6. Krystal
    April 16, 2014 at 10:07 pm

    Thank you for this information – it makes so much sense. I have a six week old and I’ve been pumping to prepare to go back to work in two weeks. I have been pumping anywhere from 3-8 oz per day in addition to nursing. He has only had a few bottles in my absence. How do I adjust my milk production back down to making only what he needs instead of being engorged until I pump? Should I be pumping on a daily basis before I go back to work or should I wait and pump at work for him to eat the following day? I have a small freezer supply already. Thank you!

    • sarah
      April 17, 2014 at 11:03 am

      I would try to schedule the pumping for every 2-3 hours depending on your level of engorgement. It’s okay to over-pump and build up an emergency supply. As your child gets older your supply will generally stabilize and you’ll be pumping less. Eventually as your child is close to or past a year or whatever your goal is, if you have a huge freezer stash you’ll make the choice to wean off of the pump and you can just continue offering your pumped milk until you run out of pumped milk and continue nursing on demand for as long as you want. Some moms choose to donate their milk if they have a huge freezer stash that they’re not using, or they keep the milk as a backup supply in case of emergency. :)

  7. Katie
    July 24, 2014 at 10:09 pm

    Thanks so much for the information! I am going back to work soon and my son will be 9 months old. Does this same rule apply for babies over 6 months? At what age do you start decreasing the amount of breast milk? I have built up a freezer stash because I may only be able to pump once while I am at work. Will pumping once while I am away from him maintain my supply enough to nurse on demand when I am with him?

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