Do you know the length of the arrow you are shooting? If you’re like most hunters, you haven’t given arrow length much thought. After all, you can shoot good groups. And you manage to hit your target most of the time. So, why worry about arrow length or how to measure arrow length?
First and foremost, arrow length can impact your accuracy. If you are shooting an arrow that is too long, you may have trouble achieving good arrow flight. Read on below to learn how to determine the right arrow length for your compound bow.
Arrow Components
Before we dive into measuring arrow length, it would be helpful to make sure everyone is on the same page about the anatomy of an arrow. This graphic below will show the various parts of an arrow.
Arrow Length
In order to safely shoot a compound bow that is propelling carbon arrows down range at nearly 300 feet per second, it is important to carefully consider the correct arrow length for your draw length and draw weight. An arrow that is even half an inch too short may fall off your arrow rest and present a safety hazard – especially if the end of the arrow is sporting a nice, sharp broadhead!
A shorter (lighter) arrow may achieve greater speeds when compared to an arrow 1-2 inches longer. But that doesn’t mean shorter arrows are always better. On the other hand, longer arrows may turn out to be too long. Arrows that are too long may present tuning challenges with your particular draw length and draw weight setup.
Finding the proper length is important for safety and will make sure you optimize your arrow’s flight.
Measuring Arrow Length
The standard method to determine arrow length is to measure from the bottom of the throat of the nock (where it meetings the bow string) to the end of the arrow shaft.
You will also see what is called a “carbon to carbon” measurement. This arrow length measurement is, you guessed it, taken from the ends of the carbon arrow shaft excluding any nock, insert, or arrow tip.
We’re not here to debate which measurement is the best, but you should be aware of each method so you can be sure your arrows are being cut to the correct arrow length. It would be a shame to order new custom arrows only to have them arrive and find out the arrow length is too short.
Proper Arrow Length
Proper arrow length is determined largely by your draw length. But that doesn’t mean that your arrow length will match your draw length.
First, the stated draw length of your bow may not be the actual measured draw length. To find your actual draw length, measure from the throat of the arrow nock (where it touches the bow string) to the grip pivot point and add 1.75 inches. Conveniently, the 1.75-inch measurement from the grip pivot point is roughly the front of the riser on most modern compound bows, so you can also use that as a measuring point if you’d like.
On most modern compound bows where the arrow rest sits well inside of the bow’s riser, your arrow length may measure slightly shorter than your draw length. Carefully inspect that your arrow will safely extend past the arrow rest when at full draw (around one inch or so).
Visiting your local archery shop to enlist the help of an experienced bow technician is a good move here.
How Arrow Length Affects Arrow Spine
Ok, you’ve checked your draw length and know that, say, a 28″ arrow will safely clear your arrow rest. Good to go, right? Not exactly…
One last thing to consider before settling on your arrow’s length is the arrow spine.
What is arrow spine?
An arrow’s spine refers to the rigidity or stiffness of the arrow shaft. Maintaining rigidity in flight (limiting the arrow’s shaft oscillating back and forth) is important to achieve the best accuracy.
You’ll notice that manufacturers label arrows in varying spines – 300, 350, 400 & 500 are some common varieties but there are many others available.
How is arrow spine measured?
The Archery Trade Association (ATA) standard for measuring static arrow spine is suspending an 880-gram (or 1.94 lb.) weight from the center of a 29-inch long arrow shaft and then using a machine to measure the deflection at that point.
The resulting deflection in inches (say .500 or .350 inches) corresponds the labeled arrow spine most arrow manufacturers use for that arrow.
How do I choose the proper arrow spine?
To choose the proper spine for your carbon arrows, consult a chart like this one from Easton Archery.
This chart will show you the correct spine for your particular compound bow setup based on draw weight, your bow’s IBO speed rating, your desired broadhead or field point weight, and arrow length. You can even use the chart to see arrow spines recommended for various arrow lengths.
If you are in between arrow spines when choosing arrows, stick to the stiffer arrow spine. It will be much easier to tune your bow with a slightly “over-spined” arrow rather than an arrow that is not stiff enough (or “under-spined”). You can also add a weighted insert or a slightly heavier broadhead to the front of your arrow to fine tune.