Baby Weight Gain: What to Expect by Age

Weight is the most frequently measured indicator of infant growth and the first to change when nutrition is inadequate or excessive. This guide covers normal weight gain patterns from birth through 24 months based on WHO and AAP standards.

Content reviewed against published WHO, CDC, AAP guidelines

Editorial policy

Last reviewed:

Key takeaways

  • Most newborns lose 5 to 7% of birth weight in the first few days and regain it by 10 to 14 days
  • Average weight gain is about 1 ounce per day (200 g/week) in the first 3 months, slowing after that
  • Babies typically double birth weight by 4 to 5 months and triple it by 12 months
  • Breastfed babies tend to gain faster in months 1 to 3 and slower in months 3 to 12 compared to formula-fed babies
  • A consistent pattern matters more than hitting exact numbers at each visit

Normal weight gain by age

Birth to 2 weeks

All newborns lose weight in the first few days after birth as they shed excess fluid and transition to feeding. A loss of 5 to 7% of birth weight is typical for breastfed babies, while formula-fed babies typically lose 3 to 5%. A loss exceeding 10% warrants evaluation. Most babies should regain their birth weight by 10 to 14 days of age. Failure to regain birth weight by 2 weeks requires a feeding assessment.

2 weeks to 3 months

This is the period of fastest weight gain. Babies typically gain 150 to 200 grams (5 to 7 ounces) per week, or about 1 ounce per day. Breastfed babies may gain even faster during this period, particularly from weeks 3 to 6 when feeding frequency typically peaks.

3 to 6 months

Weight gain begins to slow somewhat, averaging 100 to 150 grams (3.5 to 5 ounces) per week. Breastfed babies often show a more notable deceleration compared to formula-fed babies during this period, which is a normal pattern reflected in the WHO growth standards.

6 to 12 months

Weight gain continues to slow to approximately 60 to 90 grams (2 to 3 ounces) per week. The introduction of solid foods at around 6 months supplements breast milk or formula but does not initially add significant calories. Most babies triple their birth weight by around 12 months.

12 to 24 months

Toddlers gain weight much more slowly, approximately 40 to 60 grams (1.5 to 2 ounces) per week. Appetite often decreases as growth rate slows, which concerns many parents but is developmentally normal. By 24 months, most children have quadrupled their birth weight.

Average weights by age (WHO 50th percentile)

These are median (50th percentile) values from the WHO growth standards. Remember that healthy babies range widely from the 3rd to the 97th percentile.

AgeBoys (median)Girls (median)
Birth3.3 kg (7.3 lb)3.2 kg (7.1 lb)
1 month4.5 kg (9.9 lb)4.2 kg (9.2 lb)
3 months6.4 kg (14.1 lb)5.8 kg (12.8 lb)
6 months7.9 kg (17.4 lb)7.3 kg (16.1 lb)
9 months8.9 kg (19.6 lb)8.2 kg (18.1 lb)
12 months9.6 kg (21.2 lb)8.9 kg (19.6 lb)
24 months12.2 kg (26.9 lb)11.5 kg (25.4 lb)

When weight gain is too slow

Slow weight gain may indicate inadequate caloric intake, poor absorption, or increased metabolic needs. Signs that warrant evaluation include: gaining less than 20 grams per day in the first 3 months, not regaining birth weight by 2 weeks, crossing two or more percentile lines downward, or weight-for-length falling below the 5th percentile. Common causes include breastfeeding difficulties (poor latch, low supply), tongue tie, reflux, food allergies, or underlying medical conditions. Early intervention improves outcomes.

When weight gain is too fast

Rapid weight gain (consistently crossing percentile lines upward) in infancy has been associated with increased risk of childhood obesity. However, distinguishing normal rapid growth from concerning gain requires clinical judgment. Breastfed babies commonly gain rapidly in the first 3 months and this is not concerning. For formula-fed babies, ensuring responsive feeding practices (watching for fullness cues rather than encouraging the baby to finish every bottle) can help maintain appropriate weight gain. Never restrict a baby's intake without pediatric guidance.

Frequently asked questions

How much weight should my newborn gain per week?
After regaining birth weight by 10 to 14 days of age, most newborns gain approximately 5 to 7 ounces (150 to 200 grams) per week during the first month. From 1 to 4 months, average weight gain is about 5 to 8 ounces per week. Gain slows to roughly 3 to 5 ounces per week from 4 to 6 months and 2 to 3 ounces per week from 6 to 12 months.
When should my baby double their birth weight?
Most babies double their birth weight by approximately 4 to 5 months of age and triple it by 12 months. Premature babies may take longer to reach these milestones. These are general guidelines; your pediatrician will evaluate your baby's growth in the context of their overall health and feeding pattern.
Is my baby gaining too much weight?
Rapid weight gain in infancy (consistently crossing percentile lines upward) has been associated with increased obesity risk later in childhood. However, during the first 6 months, breastfed babies in particular may gain rapidly and this is considered normal. Discuss concerns with your pediatrician, who can assess weight-for-length and overall growth pattern. Restricting a baby's intake is not recommended without medical guidance.
Does my baby's weight gain slow down after starting solids?
Some babies experience a temporary plateau or slight slowdown in weight gain when starting solids around 6 months, as they adjust to new foods and may initially eat small amounts. This is usually temporary. If weight gain continues to be slow beyond a few weeks of solid food introduction, discuss feeding strategies with your pediatrician.
Should I weigh my baby at home?
Home weighing is generally unnecessary for healthy, full-term babies who are seen regularly by their pediatrician. Daily or weekly home weighing can increase parental anxiety. However, your pediatrician may recommend home weighing if there are specific concerns about weight gain, particularly in the early weeks of breastfeeding or for premature babies.

Bottom line

Baby weight gain follows a predictable pattern: rapid gain in the first few months that gradually slows throughout the first year. The numbers in this guide are averages. Your baby's healthy weight gain depends on their individual genetics, feeding method, and overall health. Consistent tracking at well-child visits is the best way to ensure your baby is gaining appropriately.

Trust your instincts. If something feels wrong, reach out to your pediatrician. Worrying about your baby means you care — that is a good thing.

All content follows our editorial policy and is reviewed against published clinical guidelines.

2,705 evidence-based guides6 authoritative medical sources