Arrow Speed
Calculate arrow speed with the IBO formula. Free archery calculator for bow speed, kinetic energy, and momentum from draw length, draw weight, and arrow weight.
About This Calculator
The Arrow Speed Calculator helps archers, bowhunters, and sports enthusiasts determine the speed of an arrow based on the International Bowhunting Organization (IBO) specification. By entering your bow's IBO rating, draw length, draw weight, arrow weight, and any additional string weight, you can accurately estimate arrow velocity in feet per second (ft/s) and meters per second (m/s).
The calculator uses the standard IBO formula: v = IBO + (L − 30) × 10 − W/3 + min(0, −(A − 5D)/3), where L is draw length in inches, W is additional string weight in grains, A is arrow weight in grains, and D is draw weight in pounds. This formula accounts for deviations from the IBO standard of 30-inch draw, 70-pound draw weight, and 350-grain arrow to give you real-world arrow speed for your specific bow setup.
Along with arrow speed, the calculator computes kinetic energy in foot-pounds and joules, and momentum in lb·ft/s — two critical metrics for understanding arrow penetration and downrange performance. Kinetic energy is calculated as KE = A × v² / 450240, and momentum as M = A × v / 7000, where A is arrow weight in grains and v is speed in ft/s.
What the Results Mean
Arrow Speed (ft/s): The primary velocity measurement. Modern compound bows typically achieve 250–350 ft/s, while recurve bows are slower at 150–225 ft/s. Higher speeds result in flatter trajectories and less wind drift.
Kinetic Energy (ft·lb): Indicates the arrow's striking energy. For deer hunting, a minimum of 25 ft·lb at impact is recommended; for larger game like elk, 50 ft·lb or more is advised.
Momentum (lb·ft/s): Reflects the arrow's ability to maintain energy through a target. Heavier arrows with good momentum are preferred for penetration on large game.
Frequently Asked Questions
What is the IBO specification for arrow speed?
The IBO (International Bowhunting Organization) specification defines a standard arrow speed measurement: a bow with 30-inch draw length, 70-pound draw weight, shooting a 350-grain arrow. The IBO rating printed on your bow represents the speed under these exact conditions. Our calculator adjusts this rating to your actual setup.
How does draw length affect arrow speed?
Every inch of draw length beyond 30 inches adds approximately 10 ft/s to arrow speed, while every inch under 30 inches subtracts 10 ft/s. Longer draw lengths store more energy in the bow limbs, resulting in higher arrow velocities. This relationship is linear within the typical range of bow operation.
How does arrow weight affect speed and kinetic energy?
Heavier arrows reduce speed but can increase momentum and penetration. The IBO formula reduces speed by 1 ft/s for every 3 grains of arrow weight above 5 times the draw weight. For example, at 70 lbs draw weight, any arrow weight above 350 grains (5 times 70) reduces speed proportionally. Lighter arrows fly faster but carry less downrange energy.
What is a good arrow speed for hunting?
For compound bows, arrow speeds of 270 to 320 ft/s are common and effective for most hunting situations. Faster arrows at 300 ft/s and above provide flatter trajectories and less wind drift. However, heavier arrows with lower speeds of 250 to 270 ft/s often provide better penetration on large game due to higher momentum.
How can I measure arrow speed without a chronograph?
You can estimate arrow speed using the distance-drop method: shoot a group at 20 yards with your 20-yard pin, then shoot at 40 yards using the same pin. Measure the vertical distance between the two groups and reference a speed chart. For example, a 15.5-inch drop between 20 and 40 yards corresponds to approximately 300 ft/s. For precise measurements, an optical or Doppler chronograph is recommended.
What factors affect arrow speed beyond the IBO parameters?
Several factors can reduce arrow speed from the calculated value: bowstring material and weight, peep sight weight, nock weight, fletching size and material, weather conditions such as humidity and rain, and overall bow efficiency. A well-tuned bow with lightweight accessories will consistently achieve speeds closer to the IBO rating.
Is the Arrow Speed Calculator suitable for recurve bows?
Yes, the calculator works for recurve and longbows as well as compound bows. Recurve bows typically have lower IBO ratings and maximum speeds around 150 to 225 ft/s. The same IBO formula applies, but recurve archers should note that their actual speeds are generally lower than compound bows of similar draw weight due to lower bow efficiency.