Background In paediatric resuscitation, for a rapid and accurate estimate of children's weight, the Broselow tape can be used in children who are 46–144 cm tall. The Broselow tape has previously been found to provide the most accurate estimate of children's weight internationally, but it is not known how many fall outside the range of the tape, or whether such children can be assumed to be of adult weight, or how otherwise to estimate the weight of these children.

Objectives To determine what proportion of children in different age groups falls outside the limits of the Broselow tape, how their weight compares with that of the adults and what correlates most strongly with weight in these children.

Methods This was a population-based prospective observational study of Chinese children up to 12 years old, from schools in Hong Kong. Weight was measured to the nearest 0.2 kg, and the height, foot-length and mid-arm circumference (MAC) were measured to the nearest 0.1 cm.

Results 40% of 10-year olds and 70% of 11-year olds were too tall for the tape. Their median weight was 41.9 kg. This was significantly less than the median weight of 18-year olds (55 kg, p<0.0001) in Hong Kong. The strongest correlate with weight in these children was MAC.

Conclusions The Broselow tape is inappropriate for use in most children over 10 years old. Children too tall for the tape cannot be assumed to be of adult weight; to do so would imply an average overestimate of 30%. Weight estimates in older children could be based on MAC.