Pedemy All toolsEnter birth weight, today’s weight and age. The percent loss, what it means and a feeding plan appear at once. For healthy term and late-preterm newborns in the first weeks.
This calculator works out how much weight a newborn has lost since birth, in grams and as a percentage of birth weight, from the birth weight, today’s weight and the age in hours or days. Weights can be entered in grams or in pounds and ounces. It then reads the result against the expected pattern: most newborns reach their lowest weight around day 3 to 4 and are back to birth weight by 10 to 14 days. Breastfed babies lose more than formula-fed babies, and babies born by cesarean lose more than those born vaginally.
Loss of 7% or more prompts a feeding assessment: watch a full feed, check latch and milk transfer, count diapers and offer lactation support. Loss of 10% or more is a signal for a full evaluation the same day, including signs of dehydration, jaundice and, when indicated, serum sodium and bilirubin. Following ABM Clinical Protocol #3 (revised 2017), 10% loss is not an automatic reason to give formula; supplementation is decided after that evaluation. For an hour-specific percentile, the page links to the Newborn Weight Tool (Flaherman et al., Pediatrics 2015).
The feeding plan section lists the expected 8 to 12 breastfeeds every 24 hours, wet diapers and stools by day of life, and the ABM Protocol #3 table of average colostrum intake per feed by hour of age (2–10 mL in the first 24 hours, 5–15 mL at 24–48 hours, 15–30 mL at 48–72 hours and 30–60 mL at 72–96 hours), which guides supplement volumes. It gives the order of preference for supplements — the mother’s own expressed milk, then donor human milk, then formula — and the AAP follow-up timing of a visit within 48 to 72 hours of discharge.
Most newborns lose some weight in the first days, with the lowest point around day 3 to 4. Exclusively breastfed babies lose more than formula-fed babies, and cesarean-born babies lose more than vaginally born babies. Losing 7% or more calls for a feeding assessment, and 10% or more calls for a same-day evaluation. Compare with the hour-specific Newborn Weight Tool for a percentile.
Not automatically. ABM Clinical Protocol #3 says 10% loss is an indication to evaluate the infant, not an automatic reason to supplement. Watch a feed, examine for dehydration and jaundice, review diapers and consider sodium and bilirubin. If a supplement is needed, use the mother’s expressed milk first, then donor milk, then formula, in small volumes matched to the baby’s age.
ABM Protocol #3 lists average colostrum intakes of about 2–10 mL per feed in the first 24 hours, 5–15 mL at 24–48 hours, 15–30 mL at 48–72 hours and 30–60 mL at 72–96 hours. Feed to the baby’s cues, and have the mother express milk each time a supplement is given to protect her supply.
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