Arrow Speed Calculator
This calculator allows the user to generate and compare the estimated speeds of their desired specifications. The user has to enter the bow’s specific rating (IBO speed), draw length, draw weight, arrow weight, and additional weight on the bowstring, and our calculator will do the rest. With this calculator you can get a near to accurate idea of change in arrow speed, kinetic energy and momentum by changing the IBO specifications to decide the desired specifications for you.
Tutorial
Here is a simple guide for you.
- Input your current parameters, to find out your arrow speed, kinetic energy and momentum
- If you want to compare it with other parameters, press the compare button and enter the new values. Then press generate and a comparison will be created.
- After the limit of 5 is reached, just clear the setups if you want to try again.
- Don’t press generate multiple times as it will create a comparison with the same values.
Calculator
| Setup | IBO Speed (ft/s) | Draw Length (in inches) | Draw Weight (in pounds) | Arrow Weight (in grains) | Additional Weight (in grains) | Calculated Speed (ft/s) | Kinetic Energy (ft-lbs) | Momentum (Ns) |
|---|
How does This Calculator Work
The calculator is based on assumptions, all the values calculated are a very close idea of the actual value. Lets start by discussing what are IBO specs.
IBO Specifications
When you buy a bow there is a specific rating or speed of each bow, it is called the IBO speed which measures the speed of an arrow shot from a bow in feet per second (fps). This rating allows archers and bowhunters to make informed decisions when choosing equipment, as it provides a consistent and objective way to assess a bow’s velocity and performance. The IBO speed is a standard and is calculated for all bows with one specific setup that is
- Draw length: 30 inches
- Draw weight: 70 pounds
- Arrow weight: 350 grains
Now when you make changes to any one of these specifications, your arrow speed changes. Meaning that by setting your desired draw length, your IBO speed increases or decreases but how much? To answer that we have made some assumptions.
Fun Fact: Without the IBO specs, there would be no standard, so no calculator would have been made.
Archery Calculator Rules
The calculator is designed in such a way that it:
- Adds 10 ft/s to the IBO speed for every one inch increase in draw length above 30″, conversely it subtracts 10 ft/s from the IBO speed for every one inch decrease of the draw length below 30″.
- Adds or subtracts about 15 to 17 ft/s from the IBO speed for every 10 pound increase or decrease of draw weight respectively.
- Subtracts 1 ft/s from the IBO speed for every 3 grains increase in arrow weight above 350, similarly adds 1 ft/s to IBO speed for every 3 grains decrease in arrow weight below 350 grains. This is the assumption, ill explain in the next section.
- Adds or subtracts 1 ft/s from the IBO speed for every 3 grains increase or decrease of additional weight on bowstring
Why isn't the calculator Hundred percent accurate?
This calculator is not hundred percent accurate compared the results obtained by a chronograph. There are a few reasons for that.
Reason 1:
The biggest reason is that while the assumption of 3 grains per foot per second is a good rule of thumb for many setups near the standard specs, it becomes less accurate as you deviate further from those specifications due to the complex interaction between bow and arrow characteristics.
As arrow weight increases, the efficiency of the bow also tends to increase. In other words, a heavier arrow can transfer more energy from the bow to the arrow itself, resulting in a higher arrow speed. This relationship isn’t linear.
As an example, if we increase arrow grain by 3 above 350 grains arrow weight, 70 pounds draw weight and 30 inch draw length then yes the IBO speed will decrease by 1 ft/s. The same is not true for greater arrow weights, for example for a weight of 500 grains and rest of the specs kept the same, an increase of 3 grains might not be enough to decrease the IBO speed by 1 ft/s. It might require 4 or 5 grains.
Reason 2:
In this calculation method, the environmental factors are not a part of the equation like in other real life speed measuring methods. Temperature, wind, humidity and air density play a part in speed of arrow. So if we skip them from our measurement, it is definitely not gonna be 100% accurate. Anyways this calculator is just for you to have an idea about the speed with your desired specifications.