How much of the arrow length are you supposed to measure? From the nock center or the arrow end? To the end of the tip or to the end of the arrow (insert)?

The reason I ask is that it appears that BowJackson calculates it basically without the tip added in. I think that The Archery Program is that way also.

This measurement can make a huge difference on FOC when you use a longer broadhead (NAP Thunderhead) versus a short one (Rocket Steelhead).