The APLS formula underestimated weight in all age groups with a mean difference of -1.4 kg (95% limits of agreement 5.0 to -7.8). The Luscombe and Owens formula was more accurate in predicting weight than the APLS formula, with a mean difference of -0.4 kg (95% limits of agreement 6.9 to -6.1%). Using linear regression analysis, and simplifying the derived equation, the best formula to describe weight and age was (weight = [2.5 x age] + 8)