PREFIX SYMBOL FORTRAN yotta Y 10E+24 zetta Z 10E+21 exa E 10E+18 peta P 10E+15 tera T 10E+12 giga G 10E+9 mega M 10E+6 kilo k 10E+3 hecto h 10E+2 deka da 10E+1 deci d 10E-1 centi c 10E-2 milli m 10E-3 micro µ 10E-6 nano n 10E-9 pico p 10E-12 femto f 10E-15 atto a 10E-18 zepto z 10E-21 yocto y 10E-24 The SI replaces the mks system; note the following spellings and abbreviations in SI m = metre mL = millilitre L = litre J = joule Wb = weber N = newton W = watt Hz = hertz km = kilometre Pa = pascal The rule for units is: "If it is named for a man or woman then capitalize the abbreviation, otherwise do not capitalize the abbreviation, except for litre which is L." [Note: the litre is not truly a SI unit.] Note also that 1 Calorie = 1000 calories, i.e., 1000 cal = 1 Cal. [The calorie and Calorie are not SI units. Today, the calorie is defined as exactly 4.184 joules, and the Calorie is 4,184 J.] Note that 10 Å = 1 nm so that the wavelength of green light is about 5200 Å which is also 520 nm. [Ångstroms are not SI units.] This page was last updated: Monday, 26-Oct-2015 00:24:00 EDT April 22, 1997