The formula 'Weight=(0.5×age in months)+4' significantly overestimates the mean weight of children under 1 year admitted to PICU by between 10% and 25.4%. While the formula 'Weight=(2×age in years)+8' provides an accurate estimate for 1-year-olds, it significantly underestimates the mean weight of 2-5 year olds by between 2.8% and 4.9%. The formula 'Weight=(3×age in years)+7' significantly overestimates the mean weight of 6-11 year olds by between 8.6% and 20.7%