Keeping track of units during conversions can get confusing. therefore, a good strategy is to use dimensional analysis. in dimensional analysis, conversion factors are used to cancel out unwanted units and leave the desired units. consider the following example: how many football fields could fit on a 1 milemile stretch of land? here are the relevant conversion factors: relating miles to meters is 1 mile = 1610 m the speed of light is 3.00 times 10^8 m/s. how fast is this in miles per hour (miles/h)? the conversion factor relating feet to meters is 1 ft = 0.305