2.1 Conversion Factors

Conversion factors into and from SI units are given in Table 2.5. The table can also be used to convert from one traditional unit to another. Convenient multiples or sub-multiples of SI units can be derived by the application of the prefix multipliers given in Table 2.4. Table 2.6 gives commonly required conversions.

The majority of the conversion factors are based upon equivalents given in BS 350:Part 1:1983 'Conversion Factors and Tables'.

Throughout the conversions the acceleration due to gravity (g) has been taken as the standard acceleration 9.806 65 m s ^-1. Units containing the word force like 'pounds force' are converted to SI units using this value of g.

The B.t.u. conversions are based on the definition accepted by the 5th International Conference on Properties of Steam, London, 1956, that 1 B.t.u. lb ^-1 = 2.326 J g ^-1 exactly. Conversions to joules are given for three calories; calories (IC) is the 'international table calorie' redefined by the 1956 conference referred to above as 4.186 8 J. Calories (15 C) refers to the calorie defined by raising the temperature of water at 15 C by 1 C and calories (US thermochemical) is the 'defined' calorie used in some USA work and is defined at 4.184J exactly.

The conversions are grouped in alphabetical order of the physical property to which they relate but are not alphabetical within the groups.