Average Weight & Length for a 6-Month-Old Baby

Growth at 6 Months

At 6 months, most babies have roughly doubled their birth weight. The average 6-month-old boy weighs about 8.2 kg (18 lb) and measures 68 cm (26.7 in). Girls average about 7.5 kg (16.4 lb) and 65.9 cm (25.9 in). Growth rate begins to slow compared to the first 3 months.

Starting Solid Foods

Around 6 months, most babies are developmentally ready for solid foods — they can sit with support, show interest in food, and have lost the tongue-thrust reflex. Starting solids doesn't typically affect growth trajectory significantly in the short term. Breast milk or formula remains the primary nutrition source through the first year.

Growth Rate Changes

After the rapid growth of the first few months, growth rate naturally slows. Babies now gain approximately 400–600 grams (14–21 oz) per month in weight and about 1 cm per month in length. This is normal and expected — don't worry if the weight curve starts to flatten slightly. Use our growth velocity calculator to verify normal rates.

Is My Baby's Size Normal?

Being at any percentile from 3rd to 97th is considered within the normal range. What matters most is that your baby follows their own growth curve consistently. A sudden jump or drop of two or more major percentile lines may warrant a discussion with your pediatrician. Learn more in our when to worry guide.