Arrow Speed Calculator

Arrow speed determines much of how a bow feels and performs, but the number printed on a bow is not a promise of speed for every setup. Manufacturers publish an IBO rating measured under standardized conditions: a 70-pound draw weight, a 30-inch draw length, and a 350-grain arrow. Most archers use a different draw length, draw weight, arrow mass, and string-accessory load. This calculator starts from the IBO rating and applies common field-estimation adjustments to bridge the gap between the laboratory rating and a practical launch speed. The estimate subtracts about 1.5 feet per second for each pound below the 70-pound reference and about ten feet per second for each inch below the 30-inch reference. Arrow mass above 350 grains reduces speed by roughly 1.5 feet per second for each five extra grains. Added peep sights, silencers, and similar moving string accessories reduce speed by about one foot per second per three grains. These rules are widely used for planning, but bow efficiency, cam design, string condition, release technique, and measurement tolerances can all move an actual chronograph reading away from the estimate. Once velocity is estimated, the calculator derives kinetic energy from arrow weight and the square of speed. Kinetic energy indicates the capacity to do work and rises sharply with velocity. Momentum is proportional to mass and speed, so a heavier arrow can retain useful momentum even while traveling more slowly. Bowhunters often compare both quantities because energy and momentum describe different aspects of performance; neither number alone guarantees penetration, accuracy, or an ethical outcome. Use the result as a setup comparison rather than a substitute for a chronograph. Enter total finished arrow weight, including point, insert, shaft, nock, and fletching. Accessory weight should cover items attached to the moving string rather than the arrow itself. If you change one input at a time, the calculator clearly shows the tradeoff between a flatter trajectory and a heavier projectile. Confirm the final configuration on a properly spaced chronograph, inspect all equipment, and follow the bow and arrow manufacturers' minimum-weight and safety recommendations.