Total body water can be estimated using the following classic formulae:

For males

Total Body Water (TBW) = 2.447 - 0.09516 X age + 0.1074 X height + 0.3362 X weight

Water in Litres
Age in years
Height in cm
Weight in kg

For females

TBW = -2.097 + 0.1069 X height + 0.2466 X weight

Water in Litres
Height in cm
Weight in kg

References

Watson PE, Watson ID, Batt RD.
Total body water volumes for adult males and females estimated from simple anthropometric measurements.
Am J Clin Nutr. 1980 Jan;33(1):27-39.