Shaft Length (in)
To determine your shaft length subtract 1in from your draw length. (Shaft Length = Draw Length - 1in)
 
IBO Speed (fps) Adjustments
DO NOT include weight adjustments to the Spine Calculator input labeled "Draw Weight". Only use these adjustments when referencing this chart.
Less than 300fps :
Subtract 5lbs from your draw weight
300-330fps :
No adjustments needed
331-351fps :
Add 5lbs to your draw weight
More than 351fps :
Add 10lbs to your draw weight