Newborn Weight Loss & Regain Calculator

See how your newborn's current weight compares to their birth weight — as a percentage, and as an average gram-per-day change.

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Compared to birth weight
days old
average g/day change
Most newborns lose some weight in the first few days after birth, then regain it by around 10–14 days old and go on to gain roughly 20–30g (about 0.7–1 oz) a day for the first few months. This is a general estimate, not a growth chart or diagnosis — your pediatrician tracks your baby's own pattern at every visit, which matters more than any single number here.

Common questions

How much weight loss is normal for a newborn?

Losing up to about 7% of birth weight in the first few days is common and generally considered normal, especially in breastfed babies while milk supply is establishing. Loss beyond about 7–10% is when pediatricians typically start looking more closely at feeding.

When should my baby regain their birth weight?

Most newborns regain their birth weight by about 10–14 days old. Regaining it a few days later than that isn't automatically a problem, but it's a common check-in point pediatricians use at the two-week visit.

How many grams per day should my newborn gain?

Once past the initial weight-loss period, a commonly cited range is about 20–30 grams (roughly 0.7–1 ounce) per day for the first three months, though this varies with feeding method, birth weight and individual growth pattern.

What if my baby has lost more than 10% of their birth weight?

Weight loss beyond about 10% of birth weight is generally considered a signal to have your baby evaluated promptly — it can point to feeding difficulties (latch, milk transfer, supply) or other issues that are usually very manageable once identified. Contact your pediatrician rather than waiting for the next scheduled visit.

Is this the same as the growth percentile calculator?

No — this tool compares your baby's current weight only to their own birth weight, to see the direction and rate of change. Our Growth Percentile Calculator instead compares a measurement to the wider population of babies the same age, which is a different (and complementary) way of looking at growth.