This calculator will estimate the speed of the bow/arrow based on the speed rating of the manufacturer and individual setup of the bow. Archers can use this calculator to get an approximate idea of how changing the bow from IBO/ATA specifications (30″ draw length, 70 lb. draw weight, 350 grain arrow) will affect the speed.

For more information on estimating speed, please see the How to Estimate Bow/Arrow Speed article

Enter IBO rating for the bow (FPS)

Enter actual draw length of the bow (inches)

Enter peak draw weight (pounds)

Enter total arrow weight (grains)

Enter additional weight on the string (grains)

Estimated FPS =

Note: This calculator makes the assumption that increasing or decreasing arrow weight by 3 grains will change the speed by one foot per second. As arrow weight increases, bow efficiency also increases. As a result, as arrow weight increases much beyond IBO/ATA specs of 5 grains per pound of bow draw weight (350 grain arrow at 70 lbs. draw weight) most bows will change one foot per second with added arrow weight of more than three grains. For example, a 70 lb. bow may lose one foot per second for every additional three grains of arrow weight for arrows near 350 grains, but for arrows near 450 grains it may take 4 grains of arrow weight to reduce the speed one foot per second.