We know that the ‘APLS formula’ is inaccurate as a tool for estimating weight in Western children, and British and Australian researchers have devised more fitting formulae for their local populations as described here.

The emergency medicine team at the Accident and Emergency Medicine Academic Unit, Chinese University of Hong Kong have now provided a solution for Chinese children:

weight (kg) = (3 x age) + 5.

This was most accurate and precise in children <7 years old.
Age-based formulae to estimate children’s weight in the emergency department
Emerg Med J. 2010 Oct 13. [Epub ahead of print]