General information from published guidance, not a diagnosis or medical advice for your baby. If you are worried, call your doctor, midwife or local health line, whatever this page says. In an emergency, call your local emergency number.
Work out the weight change
Save this weight in Ella and see it on the WHO growth chart.Open Ella
Get medical help now if
your baby is very sleepy, floppy or hard to wake for feeds10
If your baby stops breathing, turns blue or grey, is floppy or cannot be woken, call your local emergency number now.
The details
Why newborns lose weight
In the first days babies lose extra fluid, pass meconium and take only small amounts of colostrum. That is why a small drop is expected. As milk volume increases, usually between days 2 and 5, weight starts to climb again.
Breastfed babies tend to lose a little more than formula-fed babies. If you had a lot of IV fluids in labor, your baby may be born carrying extra fluid. Losing it can make the drop look bigger than it really is.
From about 2 weeks to 3 months, babies typically gain 20-40 g a day, around 150-300 g a week. Gain slows down after 3-4 months. Your doctor will plot your baby on a growth chart: following a curve matters more than any single number. See how growth percentiles work.
A big weight loss is usually about feeding, not illness. A midwife, lactation consultant or doctor can check the latch, feeding frequency and milk transfer, and make a plan. Asking early makes a real difference.
Most babies lose about 5-7%. The AAP says a well-fed newborn loses no more than 8-10%; above 10%, NICE advises a check by your midwife or doctor.25712
When do newborns regain their birth weight?
Most babies are back to birth weight by 10-14 days. If your baby isn't by 2 weeks, talk to your doctor or midwife.126
How do I calculate my baby's weight loss percentage?
Subtract today's weight from birth weight, divide by birth weight and multiply by 100. For example, from 3,500 g to 3,290 g is a 6% loss. The calculator on this page does it for you.
How much weight should a baby gain per week?
After the first 2 weeks, about 150-300 g (5-10 oz) a week is typical until 3 months, then gain gradually slows.86
Ella
Every weigh-in on a WHO growth chart
Log weight and length in Ella and see them on the WHO growth curves, with percentiles, in the app and the browser.
Guidance can differ between countries. Where it does, we show both. Follow your own doctor or health service.
Checked against current guidance on October 8, 2026. General information, not medical advice. Written by the Ella team at Muchita AI from published guidance by the AAP, NHS, NICE, WHO and CDC, with AI-assisted drafting and translation checked against those sources by our team. These organisations have not reviewed or endorsed this page. General information, not a diagnosis or medical advice. If you are worried about your baby, trust your instinct and call a doctor.
