If you are looking for a spare bar for your chainsaw, you need to determine its bar size. You will measure the used length of the bar. To determine the required length of the chainsaw bar, measure it from the front end to the cutter closest to the saw body. Round this measurement to the nearest even number in inches.  For example, a part that measures 18 3/4 will actually have a named length of 20 ". You can then find a new part with a length of 20. You can also enter this dimension in the Bar and Chain Calculator to find the correct bar replacement for your chainsaw.