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