Weight-for-Length Percentile Calculator (WHO, 0-24 Months)

How Weight-for-Length Percentiles Work

Weight-for-length percentiles assess whether a child’s weight is proportionate to their length, regardless of age. This is especially useful for identifying children who may be underweight or overweight relative to their body size, rather than simply comparing to age-based norms.

The WHO uses the LMS method to model the distribution of weight at each length value. The chart covers lengths from 45 cm to 110 cm, which corresponds roughly to birth through 24 months for most children.

Example Calculation

A boy who is 70 cm long and weighs 6.0 kg would be approximately at the 50th percentile for weight-for-length, since the WHO median weight for boys at 70 cm is about 6.04 kg. This means his weight is proportionate to his length.

Frequently Asked Questions

How is weight-for-length different from weight-for-age?

Weight-for-age compares a child’s weight to other children of the same age. Weight-for-length compares weight to other children of the same body length, which better assesses whether the child’s weight is proportionate to their size. A tall child may be heavy for their age but perfectly proportionate for their length.

When should I use weight-for-length vs. BMI?

The WHO recommends weight-for-length for children under 2 years (measured lying down) and BMI-for-age for children aged 2 and older (measured standing). Weight-for-length is preferred for younger children because BMI can be less reliable at very young ages.

What length range does this calculator cover?

This calculator uses WHO data covering lengths from 45 cm to 110 cm, which spans roughly from birth through 24 months for most children. Lengths outside this range are not covered by the WHO weight-for-length growth standards.

Should I measure length or height?

For children under 2 years, use recumbent length (measured lying down). Standing height is typically about 0.7 cm shorter. If you only have standing height, you can add 0.7 cm to approximate recumbent length for this chart.