Arrow Speed Calculator

Chasing Speed: Understanding Arrow Flight Physics

For modern archers—whether bowhunters or 3D target shooters—speed is a constant obsession. A faster arrow flies flatter, minimizing the margin for error when judging distance. It also delivers kinetic energy more efficiently to the target. However, the speed printed on your bow's limb sticker is rarely the speed you will see on a chronograph. This calculator helps you estimate the real-world performance of your setup by adjusting the manufacturer's IBO rating for your specific variables.

What is IBO Speed?

The International Bowhunting Organization (IBO) set a standard so consumers could compare apples to apples when buying bows. An IBO speed rating measures a bow produced under very specific, "best-case" conditions:
- Draw Weight: 70 lbs +- 2 lbs.
- Draw Length: 30 inches.
- Arrow Weight: 350 grains (5 grains per pound of draw weight).

If your personal setup differs from these specs (and it almost certainly does), your arrow will be slower than the rating.

Factors That Kill Speed

Every time you deviate from the IBO standard, you likely lose Feet Per Second (FPS).

1. Arrow Weight (The Biggest Factor):
Basic physics dictates that a heavier object requires more force to accelerate. For every grain of weight you add above the IBO standard (350 grains), you lose speed. A general rule of thumb used by archery technicians is that you lose 1 FPS for every 3 grains of added arrow weight.

2. Draw Length:
A shorter power stroke means less time for the string to transfer energy to the arrow. You typically lose about 10 FPS for every inch your draw length is below 30 inches. Conversely, long-draw archers (31"+) might actually exceed IBO speeds.

3. Draw Weight:
Lowering the poundage reduces the stored potential energy in the limbs. You lose roughly 2 FPS for every pound of draw weight reduced below 70 lbs.

4. String Accessories:
Peep sights, silencers, and d-loops add weight to the string itself. Weight on the center of the string acts like a brake. A loaded string can cost you 5-15 FPS depending on how much hardware you install.

Speed vs. Momentum: The Hunter's Dilemma

While speed is great for a flat trajectory, it isn't the only metric that matters, especially for hunting. A light, fast arrow might look cool on a chronograph, but a heavier, slower arrow carries more momentum. Momentum is what drives an arrow through bone and tissue.

- Target Archers: Often prioritize speed for flatter trajectory (forgiveness in range estimation).
- Hunters: Often seek a "Goldilocks" balance—heavy enough to penetrate, but fast enough to minimize string jumping by the deer.

Using This Calculator

Enter your bow's advertised IBO speed, your current draw weight, and your total arrow weight (including point, insert, fletching, and nock). The calculator uses standard deductions to give you a realistic estimate of what you would see if you shot through a chronograph today.