If your target is to find how fast an arrow travels, then you aim right because the arrow speed calculator will easily help you with that 🏹 With this archery calculator, you'll also be able to identify the different factors and what values can help you improve your arrow's speed.

We've created a text where you'll find some of the basics related to IBO speed and how to calculate bow speed. This is what we included:

  • What is IBO speed?:
  • Which are the factors that affect arrow speed?; and
  • How to calculate the fps speed of an arrow, its momentum, and kinetic energy.

Let's get started! 🎯

What is IBO speed? — Arrow speed specification

The IBO speed is used as a standardized speed rating for bows. Created by the International Bowhunter's Organization, the IBO speed is given as a speed value in feet per second (fps or ft/s), and the higher this number is, the higher the speed that could be achieved with that particular bow. For example, a bow designated as IBO 330 could achieve greater speeds than a bow rated as IBO 300.

And we purposefully say "speed that could be achieved" because these marked speeds are not usually the ones that an archer can attain while using his bow with his specific setup. This is because the IBO speeds are determined under a set of particular conditions:

  • Draw length equal to 30 inches;
  • Draw weight equal to 70 pounds; and
  • Arrow is weighing 350 grains.

Then, for comparing bow speeds, you'll need to maintain these factors constant. But because these are rarely the conditions under which every archer will be using their bow, then comes the question: what the actual speed of my arrow is? 🏹

Which factors affect on arrow speed?

Before we see how to calculate bow speed, let's go through the main factors that influence the arrow speed to better understand how the actual speed is determined:

  • Draw weight DD — This is the force required to pull a bow, expressed in pounds. Then, the more draw weight you use to pull, the quicker an arrow will fly and the more kinetic energy it will have. As a general rule, with every 10 pound increase in draw weight, arrow speed rises by around 20 fps.

  • Draw length LL — This is the distance that the string is pulled back. A longer draw length results in a longer power stroke than a shorter draw length, allowing the bow to store more energy that then is transferred to the arrow. The general guideline for this factor is:

    • For every extra inch of draw length increases approximately 10 fps the arrow speed; and

    • For every inch you reduce, the draw length reduces around 10 fps of your bow speed.

  • Arrow weight AA — If you guessed that the size and weight of an arrow influence its speed, you're correct. As you might expect, a heavier arrow flies slower than a smaller and lighter one.
    When it comes to how much an arrow's weight affects its speed, the consensus is that every additional 5 grains of arrow weight reduces arrow speed by an average of 2 fps.

  • Bowstring weight WW — Adding accessories to a bowstring impacts its speed; for every 3 grains of extra weight on the bowstring, deduct 1 fps from the IBO number.

Calculate arrow fps speed — How fast does my arrow travel?

All of these parameters are summarized in an equation that you can use to estimate the actual arrow speed:

v= IBO+(L30)×10W ⁣/3 +min(0,(A5D ⁣/3))\small \begin{align*} v =\ &\text{IBO} + (L - 30) \times 10 - W\!/3\ +\\ &\min(0, -(A - 5D\!/3)) \end{align*}

where:

  • vv — Actual arrow speed in ft/s (fps);
  • IBO\text{IBO} — Standard arrow speed in terms of IBO specifications in ft/s (fps);
  • LL — Draw length in inches;
  • WW — Additional weight on the bowstring in grains;
  • AA — Arrow weight in grains; and
  • DD — Draw weight in pounds.

With this archery calculator, you can also find the momentum and kinetic energy of an arrow. The momentum of an arrow is linked to arrow penetration. You can obtain this value with this formula:

momentum=A×v\small \text{momentum} = A \times v

An arrow's kinetic energy is determined as:

kinetic energy=A×v22\small \text{kinetic energy} = \cfrac{A \times v^2}{2}

Keep in mind that the arrow loses speed as it travels. Thus these values of speed, momentum, and kinetic energy, are only valid within a specific distance range. To find the distance that your arrow will travel, you can use the projectile motion calculator.

It's also worth noting that these variables are affected not just by the arrow's speed vv but also by its mass AA. And the greater the mass, the longer the energy stays in the arrow as it flies. However, here you'll find a bit of a contradiction because heavier arrows result in slower speeds, meaning compromising speed might be necessary to avoid losing momentum and kinetic energy so rapidly.

🙋 If you want to learn more about momentum and how to calculate it, we have a dedicated momentum calculator that you might enjoy!

How to use the arrow speed calculator

The arrow speed calculator makes it easy to estimate the speed of an arrow! By simply indicating the particular values of some parameters, this tool will help you calculate an arrow fps speed. Let us see how to use this tool:

  1. Begin by indicating the IBO rating in fps in the Bow IBO rating field.

  2. Now, enter the Draw length of the bow.

  3. Indicate the Peak draw weight.

  4. Next, input Arrow weight.

  5. Finally, enter the Additional weight on the string if this is known.

  6. After you've entered these values, the calculator will display the actual arrow speed, momentum, and kinetic energy of the arrow 🎯

Gabriela Diaz
Bow IBO rating
ft/s
Draw length of the bow
in
Peak draw weight
lb
Arrow weight
gr
Additional weight on string
gr
Arrow speed
ft/s
Momentum
Ns
Kinetic energy
ft-lbs
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