Weight for girls at 20 months

At 20 months, the median weight for girls on the WHO Child Growth Standards is 10.6 kg (23 lb 8 oz): half of girls this age weigh less and half more. The middle half of girls, from the 25th to the 75th percentile, falls between 9.81 and 11.6 kg, a spread of 1.77 kg. The outer lines of the chart, the 2nd and 98th percentiles, sit at 8.39 and 13.7 kg.

Since 19 months, the median has risen by 0.21 kg in one month. By 21 months it reaches 10.9 kg. That monthly change is less than half the 0.96 kg of the first month, because growth slows steadily through the first two years.

For boys at 20 months the median is 11.3 kg, 0.70 kg more than for girls, which is why the charts are drawn separately by sex.

On the older CDC 2000 infant charts, which some clinics and websites still use before age 2, the median at 20 months is 11.4 kg. A girl exactly on the WHO median would read as about the 26th percentile there, one reason two charts can give different answers for the same weight.

Reading the table: a girl at 20 months who weighs 11.2 kg is at about the 66th percentile, meaning that out of 100 girls this age, about 66 weigh less.