The bar measurement of a chainsaw is different than the actual bar length. The bar measurement is important to know when you're replacing a chain or purchasing a replacement bar. The bar measurement expresses the effective cutting length of the chainsaw, not the entire length of the bar, which is actually a few inches longer than the cutting length. If you want to know the bar's true length, you'll need more than a tape measure.
Turn the chainsaw off and remove the spark plug wire from the plug itself. Grasp the boot that covers the spark plug and remove the wire by pulling gently on the boot. This prevents any possibility of the chainsaw accidentally starting.
Butt the end of a tape measure against the casing at the point where the bar emerges.
Stretch the tape to the opposite end of the bar and read the measurement at the farthest cutter at the tip of the bar.
Round the measurement to the nearest inch. For example, if you measured 15 7/8 inches from the casing to the cutter, you have a 16-inch chainsaw.
Remove the nuts securing the casing to the chainsaw body using a socket and ratchet.
Pull the cover off completely, exposing the entire chainsaw bar.
Stretch the tape measure from one end of the bar to the opposite end. This measurement is the actual size of the chainsaw bar, which is typically 2 to 3 inches longer than the chainsaw measurement you took in Steps 1 through 4.