Metrication: Conversion factors, symbols and definitions BASIC SI UNITS physical quantity name of unit symbol for unit length metre m mass kilogramme kg time second s electric current ampere A thermodynamic temperature degree Kelvin øK luminous intensity candela cd Symbols for units do not take a plural forin. SUPPLEMENTARY UNITS These units are dimensionless. physical quantity name of unit plane angle radian solid angle steradian DERIVED UNITS kVITH SPECIAL NAMES physical name symbol quantity of unit for unit energy joule J force newton N power watt W electric charge coulomb C electric potential difference volt V electric resistance ohm /1 electric capacitance farad F magnetic flux weber Wb inductance henry H magnetic flux density tesla T luminous flux lumen lm illumination lux lx frequency hertz Hz customary temperature, t degree Celius øC FRACTIONS AND MULTIPLES fraction prefix symbol multiple I 10 -• deci d 10 10 -2 centi c 10 2 10 -3 milli m 103 10 -6 micro g 106 10 -9 nano n 109 l0 -12 pico p 1012 10 -15 femto f 10 -18 atto a symbol for unit rad sr Restricted to instances where there is a strongly felt need. physical quantity area volume density velocity angular velocity acceleration pressure kinematic viscosity, diffusion coefficient dynamic viscosity electric field strength magnetic field strength luminance definition of unit kg m2s -z kgms-2_-- Jm -• kg m2 s -3 ---- J s -l As kg m 2 s -3 A -• • J A -• s -• kg m 2 s -• A -2 = V A -• A 2 8 4 kg -• m -2 = A s V -• kg m 2 s-2A -• = V s kgni 2s -2A -• =VsA -• kg s -2 A -• = V s m -2 cd sr cd sr m -2 cycle per second t/øC = T/øK--273.15 prefix symbol deka da hecto h kilo k mega M giga G tera T EXAMPLES OF OTHER DERIVED SI UNITS SI unit square metre cubic metre kilogramme per cubic metre metre per second radian per second metre per second squared newton per square metre square metre per second newton second per square metre volt per metre ampere per metre candela per square metre 66 symbol for unit m 2 m • kg m -• m s -• rad m 8 -2 N m -2 m 2 s-I Nsm -2 A m -• ca m -2

METRICATION 67 UNITS ALLOWED IN CONJ UNCTION WITH SI physical quantity name of unit symbol for unit definition o.t unit length paraec pc 30.87 x 10 '5 m area barn b 10 -28 m z hectare ha 10 4 m 2 volume litre 1 10 -3 m 3 pressure bar bar 103 N m -2 mass tonne t 10 3 kg = 1 Mg kinematic viscosity stokes St 10 -4 m 2 s -• diffusion coefficient dynamic viscosity poise P 10 -x kg m -• s -• magnetic flux density gauss G 10 -4 T (magnetic induction) radioactivity curie Ci 37 x 109 s-' energy electron volt eV 1.6021 x 10 -'9 J time hour h EXAMPLES OF UNITS CONTRARY TO SI, WITH THEIR EQUIVALENTS* physical quantity unit equivalent length •ngstr6m 10 -•ø m inch 0.0254 m foot 0.8048 m yard 0.9144 m area square inch 645.16 mm 2 square foot 0.092 903 m 2 square yard 0.836 127 m 2 volume cubic inch 1.638 71 x 10 -5 m 3 cubic foot 0.028 316 8 m 3 U.K. gallon 0.004 546 092 m 3 U.S. gallon 0.003 785 41 m 3 fluid ounce 28.413 1 cm 3 mass pound 0.453 592 37 kg ounce 28.349 5 g dram 1.771 85 g grain 64.798 9 mg density pound/cubic inch 2.767 99 x 104 kg m -3 pound/cubic foot 16.0185 kg m -3 concentration ounce/gallon 6.236 02 g 1-' force dyne 10- $ N poundal 0.138 255 N pound-force 4.448 22 N kilogramme-force 9.806 65 N pressure atmosphere 101.325 kN m -2 tolT 133.322 N m -2 pound (f)/sq.in. 6894.76 N m -2 ---- 6.894 76 kN m -2 inch of mercury 3386.39 N m -2 ener•,•y erg 10 -? J therm 105.506 MJ calorie (I.T.) 4.1868 J calorie (15 øC) 4.1855 J calorie (thermochemical) 4.184 J B.t.u. 1055.06 J -- 1.055 06 kJ foot poundal 0.042 140 1 J foot pound (f) 1.355 82 J power horse power 745.700 W=0.745 700 kW temperature degree Ranldne • øK degree Fahrenheit t/øF=•T/øCq- 32 * Fuller lists are to be found in Anderton, P. and Bigg, P. H. Changing to the metric system. 2nd edn. (1967). (H.M. Stationery Office, Londonk