Tools · Baby
Baby Weight Gain Calculator: Grams per Day and Week
Enter your baby's birth weight and weighings to see weight gain in grams per day and per week, the change since birth, and when birth weight was regained.
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This article is for general information and is not a substitute for professional medical advice. Always consult your pediatrician or doctor about your child.
Sources: WHO, CDC, AAP and NHS guidance. Recommendations differ between countries — for local advice see the NHS or CDC.
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Weighings (up to 6)
Enter the birth date, the birth weight in grams and at least one weighing (date and weight).
A record of numbers, not a diagnosis. Your midwife, health visitor or doctor can tell you what is right for your baby.
How to use the calculator
- Enter your baby's date of birth and birth weight in grams (check your discharge notes or your baby's health record).
- Add each weighing with its date and the weight in grams. You can add up to 6 and they do not need to be in order.
- Read the cards for the change since birth, the lowest weight in the first 14 days and when birth weight was regained, then the table for grams per day and per week between weighings.
Everything is worked out on your device and nothing is stored. To see whether a weight is typical for your baby's age and sex, use the baby growth percentile calculator.
What the numbers mean
- Change since birth = weight now − birth weight, in grams, and as a percentage of birth weight.
- Lowest in the first 14 days is the lowest percentage among your weighings in days 1–14. A weighing on every day would be needed to catch the exact lowest point.
- Back to birth weight is the first weighing at or above birth weight after one below it. The true day may be earlier, between two weighings.
- Grams per day = weight change ÷ days between two weighings. Per week = grams per day × 7. The first row compares with birth weight.
- Double birth weight appears only if a weighing is at or above twice birth weight. The calculator does not predict the date.
What the health sources say (averages and reference points, not a pass or fail)
- NHS: it is normal for babies to lose some weight in the first few days after birth. Babies are weighed in the first 2 weeks to check they are regaining birthweight, and most are at, or above, it by 3 weeks.
- NHS: a midwife or health visitor will support you if your baby loses a large amount of weight or does not regain birthweight by 3 weeks.
- AAP: all newborns lose weight in the first 7 days, gain steadily from about day 5, and are back at birth weight by about 2 weeks. Almost all have regained it by 3 weeks.
- AAP (breastfed newborns): a well-nourished newborn loses no more than 8–10% of birth weight in the first few days.
- AAP: the average newborn gains almost an ounce (28 g) a day, about 195 g a week. From 1 to 4 months babies gain about 0.7–0.9 kg (1.5–2 lb) a month on average, and the AAP notes these are only averages.
- AAP: doubling of birth weight typically happens at about 4 months, most babies have doubled it by 6 months, and the average child has tripled it by the first birthday.
If your baby was born early or small, your midwife or health visitor will tell you which figures apply. Weight loss beyond the figures above, or birth weight not regained by 3 weeks, is a reason to talk to your health visitor or doctor, not a diagnosis.
Related: Growth percentile calculator · Baby weight loss · Baby weight tracking · Baby not gaining weight
Frequently asked questions
How many grams per day or per week should a newborn gain?
The AAP says the average newborn gains almost an ounce (28 grams) a day, which is about 195 grams a week, and that babies gain between 1.5 and 2 pounds (0.7 to 0.9 kg) a month from 1 to 4 months. The AAP stresses these are only averages. Newborns lose weight first, so the first days of a record look like a drop, not a gain. Your baby's own pattern, shown by the calculator, matters more than one average, and the percentile calculator shows where the weight sits for age.
When do babies regain their birth weight?
The AAP says all newborns lose weight during the first 7 days, start gaining steadily from about day 5, are back at birth weight by about 2 weeks, and that almost all babies have regained it by 3 weeks. The NHS says most babies are at, or above, their birthweight by 3 weeks, and that a midwife or health visitor will support you if your baby loses a large amount of weight or does not regain birth weight by 3 weeks.
When does a baby double their birth weight?
The AAP gives typical timing rather than a rule: doubling happens typically at about 4 months, and by 6 months most babies have doubled their birth weight. By the first birthday the average child has tripled it. This calculator never predicts the date. It only shows the day of the first weighing at or above double birth weight, if you have entered one.
Is losing weight after birth normal?
Yes. The NHS says it is normal for babies to lose some weight in the first few days after birth. The AAP adds that all newborns lose weight during the first 7 days, and that a well-nourished breastfed newborn loses no more than 8–10% of birth weight in the first few days. If your baby has lost more than that, or you are unsure how feeding is going, talk to your midwife, health visitor or doctor.
How do I weigh my baby at home accurately?
Neither the NHS nor the AAP page used here gives a method for weighing at home, so this page does not give one either. What the NHS does say is that after the first 2 weeks a baby should be weighed no more than once a month up to 6 months, no more than once every 2 months from 6 to 12 months and no more than once every 3 months over age 1. Over a few days a small scale difference is a large part of the gain, which is why the calculator warns about gaps under a week. Your health visitor or clinic can weigh your baby on calibrated scales.
Sources: NHS: Your baby's weight and height (page last reviewed 20 September 2023) · AAP HealthyChildren.org: Your Baby's First Month: Growth & Physical Appearance · AAP HealthyChildren.org: How to Tell if Your Breastfed Baby is Getting Enough Milk · AAP HealthyChildren.org: Your Baby's Growth & Physical Development: 1 to 4 Months Old · AAP HealthyChildren.org: When Can Babies Start Solid Foods? · AAP HealthyChildren.org: Checkup Checklist: 6 Months Old · AAP HealthyChildren.org: Your Baby's Growth & Physical Development: 8 to 12 Months Old
Keep every weighing in one place. Whispie lets you log your baby's weight and height measurements for free, so you do not have to keep a list of dates and grams. WHO growth charts are in the app too.
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