This arrow speed calculator allows you to accurately determine the speed of an arrow. While it is based on the bow speed IBO specification, you can input the individual settings of your bow. It will give you a rough idea of how fast an arrow travels after changing the bow from the recommended specifications. You can use the results obtained from this archery calculator in the projectile motion calculator to analyze the arrow's path.
Understanding bow speed IBO specification
Most professional bows use the IBO (International Bowhunting Organization) specification. This specification determines the arrow speed, provided that you keep the following parameters:
- Draw length equal to 30 inches;
- Draw weight equal to 70 pounds; and
- arrow weighing 350 grains.
If you deviate from these parameters, the arrow speed will not equal the one given by the specification. Nevertheless, most archers do not use these exact parameters. This is where this bow speed calculator comes in handy; it allows you to examine how the arrow will behave under a different bow setting.
Archery calculator principles
You should adjust the arrow speed given by the IBO specification according to the following rules:
- For every inch of draw length under 30″, subtract 10 ft/s from the IBO value.
- For every inch of draw length above 30″, add 10 ft/s to the IBO value.
- For every 3 grains of total arrow weight above draw weight multiplied by 5, subtract 1 ft/s from the IBO value.
- For every 3 grains of additional weight on the bowstring, subtract 1 ft/s from the IBO value.
All of these rules can be put in one common equation:
- – Actual arrow speed in ft/s;
- – Arrow speed according to the IBO specification in ft/s;
- – Draw length in inches;
- – Additional weight on the bowstring in grains;
- – Arrow weight in grains; and
- – Draw weight in pounds.
You can also use the arrow speed calculator to find the momentum and the kinetic energy of the arrow. These are calculated as follows:
How fast does an arrow travel?
Let's consider the following example: you are analyzing the bow of IBO 300. You want to know the arrow's speed when you increase both the draw length and the arrow weight.
- Choose the draw length. Let's say it is equal to 32".
- Decide on the draw weight and the arrow weight. Let's say you keep the regular peak draw weight of 70 lbs but use arrows weighing 400 grains.
- If there is any additional weight on the bowstring, write it down. Let's assume this weight is equal to 5 grains.
- Input all of these values into the formula for arrow speed:
What device measures arrow speed?
You can measure arrow speed using optical chronographs, Doppler chronographs, or laptop-based audio applications. In general, all three methods can be used with equal success as there is little difference in measured speed. The optical chronograph is insensitive to shooting distance, but shooting errors can destroy the chronograph. The Doppler chronograph is fast and easy to use.
How can I calculate arrow speed without a chronograph?
Use the following method:
- Fire a group of arrows from 20 yards using the pin set for this distance.
- Mark the center of the group as a reference point.
- Change the distance to 40 yards and shoot another group of arrows to the same pin you used from 20 yards.
- Mark the center of the group and measure the distance between the two groups.
Now check the distance and estimate the speed below:
How fast can an arrow travel?
If you are using a recurve bow, arrows can travel at up to 225 feet per second (fps) or 150mph, while arrows from a compound bow travel at up to 300 fps (200mph). Heavy longbow arrows will move slower due to their weight.
What affects arrow speed?
Arrow speed depends on several factors, including bow string weight, string length, string material, arrow weight, and weather conditions. Moisture and rain will slow the arrow's flight. Fast-flying arrows have flatter flight trajectories and less deviation from the wind.
How does draw weight affect arrow speed?
The greater the draw weight, the greater the speed of the arrow shot from the bow. This is because the large draw weight imparts more energy to the arrow. For example, if you increase the draw weight by 5 pounds the speed of your arrows can increase by 10 fps. Be careful with increasing string weight, as it is equally important to string the bow comfortably.