Baby Weight Gain Calculator (Grams per Day & Ounces per Week)

How it works

gain per day = (latest weight − earlier weight) ÷ days · gain per week = gain per day × 7 · typical weekly gain: 0–4 months 155–240 g (5.5–8.5 oz) · 4–6 months 113–170 g (4–6 oz) · 6–12 months 57–113 g (2–4 oz)

After regaining birth weight, babies gain fastest in the first months — roughly 150–240 g (5.5–8.5 oz) a week until about 4 months — and growth then slows to around 110–170 g a week at 4–6 months and 60–110 g a week in the second half of the first year. These ranges, used by lactation consultants and based on WHO growth data, are guides: a single weigh-in can be off by a feed or a diaper, so compare weights on the same scale, a week or more apart, and look at the trend on a growth chart.

Worked example

A 2-month-old weighed 4.2 kg four weeks ago (28 days) and 5.0 kg today: 800 g ÷ 28 = 28.6 g per day, or 200 g (7.1 oz) per week. That is within the typical 155–240 g a week for 0–4 months.

Sources: WHO child growth standards — weight velocity · KellyMom: Average weight gain for breastfed babies

Frequently asked questions