Arrow Speed Calculator
Estimate real-world arrow speed from your bow's IBO rating and setup, then calculate kinetic energy and hunting class.
🏹 What is the Arrow Speed Calculator?
Arrow speed is the single most important number in archery and bowhunting because it determines everything downstream: trajectory, range compensation, kinetic energy delivered to the target, and penetration depth. The IBO speed printed on your bow is measured under ideal lab conditions that almost no hunter actually shoots, so this calculator closes the gap between the manufacturer's claim and what your arrow is really doing downrange.
The Speed Estimator mode uses the industry-standard IBO correction formula: start with the rated IBO speed, add 2 fps for every pound of draw weight above 70 lb (or subtract 2 fps below), add 2 fps for every inch of draw length above 30 inches (or subtract below), and subtract 1 fps for every 5 grains your total arrow weight exceeds the 350 grain standard. The result is an accurate approximation of your actual arrow speed without needing a chronograph.
The KE and Momentum mode takes a known speed from a chronograph and computes kinetic energy using the formula KE = (gr x fps squared) / 450240, expressed in foot-pounds. It also calculates momentum, which governs penetration through bone and hide, and classifies your setup into a hunting game tier based on widely accepted bowhunting thresholds.
Bowhunters use this tool to verify their setup before season opens, to evaluate how arrow changes affect performance, and to confirm they meet ethical minimums for the game they are pursuing. Students and archery coaches use it to understand the physics of projectile energy and how small changes in equipment compound into meaningful differences at the target.
📐 Formula
Speed (fps) = IBO + 2(W − 70) + 2(L − 30) − (G − 350) ÷ 5
IBO = manufacturer-rated bow speed at 70 lb / 30 in / 350 gr
W = actual draw weight in pounds
L = actual draw length in inches
G = total arrow system weight in grains (arrow + accessories)
Example: IBO 320 fps, 65 lb, 28 in, 420 gr: 320 + 2(65-70) + 2(28-30) - (420-350)/5 = 320 - 10 - 4 - 14 = 292 fps
KE (ft-lb) = (gr × fps²) ÷ 450,240
gr = arrow total weight in grains
fps = arrow speed in feet per second
Example: 420 gr at 292 fps: (420 x 85264) / 450240 = 79.5 ft-lb (elk class)
Momentum = (gr × fps) ÷ 225,400
gr = arrow total weight in grains
fps = arrow speed in feet per second
Example: 420 gr at 292 fps: (420 x 292) / 225400 = 0.5439 slug-ft/s
📖 How to Use This Calculator
Speed Estimator Mode
1
Enter your bow's IBO speed - Find the IBO speed in your bow's manual or on the manufacturer's website. Common compound bow IBO ratings range from 280 to 360 fps.
2
Set your actual draw weight and draw length - These differ from the IBO standard (70 lb / 30 in) for most hunters. Both have a 2 fps impact per unit deviation.
3
Enter arrow weight and accessories - Enter the arrow shaft weight in grains, then add broadhead, insert, wrap, and vane weight in the accessories field. Every 5 gr above 350 costs 1 fps.
4
Read your estimated speed and hunting class - The results show your real-world fps, kinetic energy, and which game tier your setup qualifies for per standard bowhunting guidelines.
💡 Example Calculations
Example 1 - Typical Whitetail Deer Setup
IBO 330 fps bow, 65 lb draw, 28.5 in draw, 425 gr arrow
1
Draw weight correction: 65 - 70 = -5 lb, x2 = -10 fps
2
Draw length correction: 28.5 - 30 = -1.5 in, x2 = -3 fps
3
Arrow weight correction: (425 - 350) / 5 = 15 fps penalty
4
Estimated speed: 330 - 10 - 3 - 15 = 302 fps
5
KE = (425 x 302 x 302) / 450240 = 85.9 ft-lb (Elk/Bear class)
Result = 302 fps, 85.9 ft-lb - Elk / Black Bear class
Try this example →Example 2 - Youth / Women's Light Setup
IBO 300 fps bow, 45 lb draw, 26 in draw, 350 gr arrow
1
Draw weight correction: 45 - 70 = -25 lb, x2 = -50 fps
2
Draw length correction: 26 - 30 = -4 in, x2 = -8 fps
3
Arrow weight correction: (350 - 350) / 5 = 0 fps (exactly 350 gr)
4
Estimated speed: 300 - 50 - 8 - 0 = 242 fps
5
KE = (350 x 242 x 242) / 450240 = 45.4 ft-lb (Elk class, just above deer minimum)
Result = 242 fps, 45.4 ft-lb - Elk / Black Bear class
Try this example →Example 3 - Known Speed with KE and Momentum (Chronograph Reading)
Chronograph reads 278 fps with a 500 grain arrow
1
Switch to KE and Momentum mode
2
KE = (500 x 278 x 278) / 450240 = 85.7 ft-lb
3
Momentum = (500 x 278) / 225400 = 0.6167 slug-ft/s (high penetration)
Result = 85.7 ft-lb, 0.617 slug-ft/s - Large / Dangerous Game class
Try this example →❓ Frequently Asked Questions
What is IBO speed and why is it always higher than my actual speed?
IBO speed is measured at exactly 70 lb draw weight, 30 inch draw length, and 350 grain arrow weight with no accessories. Most hunters shoot lighter draw weights, shorter draw lengths, and heavier arrows with broadheads and accessories. Each of these deviations reduces speed. A 65 lb / 28 in / 420 gr setup on a 330 fps IBO bow will typically shoot around 297 fps.
How accurate is the IBO speed correction formula?
The formula is accurate within 3 to 8 fps for most modern compound bows. Cam design, limb efficiency, and string material cause bow-to-bow variation. A chronograph remains the most accurate way to measure actual speed, but this calculator gives an excellent estimate when no chronograph is available.
What kinetic energy do I need for deer, elk, and bear?
Widely cited benchmarks: under 25 ft-lb for small game, 25 to 41 ft-lb for whitetail deer (42 ft-lb minimum recommended), 42 to 64 ft-lb for elk and black bear, and 65 ft-lb or more for large or dangerous game. These are guidelines, not regulations. Shot placement and broadhead sharpness also play a large role in ethical harvest.
Does a heavier arrow always have more kinetic energy?
Not necessarily. KE = (gr x fps squared) / 450240. Speed is squared, so a significant speed loss from a heavier arrow can reduce KE even though mass increased. For example, 300 gr at 320 fps = 68.1 ft-lb, but 500 gr at 250 fps = 69.4 ft-lb. Heavier arrows usually have higher momentum and penetrate deeper, but KE comparison requires calculating both.
What is arrow momentum and how is it different from kinetic energy?
Kinetic energy (ft-lb) measures the total energy available to drive penetration. Momentum (slug-ft/s) measures resistance to deceleration inside the target. A heavy, slow arrow can have the same KE as a light, fast arrow but higher momentum, meaning it drives deeper through bone and hide. Many experienced hunters prioritize momentum for large game over raw KE.
How much does draw weight affect arrow speed?
About 2 fps per pound of draw weight, above or below 70 lb. Dropping from 70 to 60 lb loses approximately 20 fps. Increasing from 70 to 75 lb adds about 10 fps. These corrections apply to modern compound bows. Traditional longbows and recurves have different efficiency characteristics.
What is the effect of draw length on bow speed?
Approximately 2 fps per inch of draw length, above or below 30 inches. A 28 inch draw is about 4 fps slower than the IBO standard; a 31 inch draw is about 2 fps faster. Draw length also affects arrow spine requirements, so changes should be matched with appropriate arrow selection.
How much do accessories add to arrow weight?
Typical weights: fixed-blade broadhead 85 to 150 gr, mechanical broadhead 60 to 125 gr, insert 15 to 50 gr, nock 8 to 15 gr, wrap 10 to 15 gr, and three vanes 10 to 30 gr total. A fully assembled hunting arrow is often 50 to 150 gr heavier than the bare shaft weight. Each additional 5 gr costs about 1 fps.
Should I prioritize speed or arrow weight for bowhunting?
For most hunting situations, a heavier, slower arrow in the 400 to 500 grain range at 250 to 290 fps provides better penetration, quieter shot, less wind drift, and more forgiveness on marginal shots than a light, fast arrow. Speed is valuable for flat trajectory at longer ranges. Most elk hunters prefer 65 ft-lb or more with high momentum over maximum fps.
What is AMO speed versus IBO speed?
AMO (Archery Manufacturers Organization, now ATA) measures speed at 60 lb draw weight, 30 inch draw length, and a 540 grain arrow. IBO uses 70 lb / 30 in / 350 gr. IBO ratings are typically 20 to 30 fps higher than AMO ratings for the same bow. Always confirm which standard your bow's speed rating uses before applying corrections.
How does temperature affect arrow speed?
Cold temperatures make bow limbs stiffer and string material less elastic, reducing stored energy and arrow speed by 2 to 5 fps on very cold days (below 20 F). Lubricating cables and checking timing in cold weather helps maintain consistent performance. The speed correction in this calculator does not account for temperature, so cold-weather hunters may see slightly lower actual speeds.
Can I use this calculator for recurve or traditional bows?
The IBO correction formula is designed for modern compound bows with cams and let-off. Traditional bows do not have an IBO rating. For recurve and longbow speed estimates, use a measured speed from a chronograph and enter it directly in the KE and Momentum mode to calculate kinetic energy and hunting class.