Table 2: Median values for hydration, density, and constants ( and ) for the paediatric version of Siri’s (11) equation, obtained by using the LMS (lambda-mu-sigma) method*.

AgeMalesFemales
Hydration %Density kg/L Hydration %Density kg/L

5 y76.51.08275.364.9576.71.08375.334.92
6 y76.31.08445.324.9076.11.08655.274.85
7 y76.11.08615.284.8675.51.08875.224.79
8 y75.91.08775.244.8275.21.09005.194.76
9 y75.71.08895.214.7975.11.09095.174.74
10 y75.51.09005.194.7675.01.09165.154.72
11 y75.31.09115.164.7375.01.09245.134.70
12 y75.21.09175.154.7274.91.09375.104.67
13 y75.01.09205.144.7174.61.09545.074.63
14 y74.81.09275.134.6974.41.09755.024.58
15 y74.41.09425.094.6674.11.09964.984.53
16 y74.01.09605.054.6173.81.10114.954.49
17 y73.71.09785.024.5773.71.10204.934.47
18 y73.51.09914.994.5473.61.10274.924.46
19 y73.41.10004.974.5273.61.10314.914.45
20 y73.31.10064.964.5173.61.10354.904.44

*C1 is calculated as ( * )/( ), and is calculated as DFFM /( ); and represent fat-free mass density and fat mass density, respectively. % fat mass is calculated as [( /Db) – ] * 100, where Db is measured body density. Adapted from Wells et al. [33].