When attempting to set up a compound bow, for best possible fitment, there are several steps, measurements, and calculations that must be accounted for. Of these various factors, few are as important as that of your bow’s draw length. In order to set this crucial adjustment, one must first know how to measure draw length.
While the process of measuring your specific draw length is seldom difficult, there are a number of key steps that must be adhered to.
What is Draw Length?
Draw length is most simply described as the distance between a bow’s riser and the most distant part of a bow’s string when at full draw.
This measurement is typically taken from the forward-most part of a bow’s grip to the point of pull on the bowstring.
The ATA (Archery Trade Association) specifies draw length in a somewhat broader sense when designating how compound bows are to be marketed.
According to the ATA, “Draw length is the distance at the archer’s full draw, from the nocking point on the string to the pivot point of the bow grip plus 1 3/4 inches.”
The draw length of a particular bow is of significance, due to the fact that it must be set specifically to each individual archer.
Every archer has their own correct draw length, which can differ substantially from that of the next individual.
This draw length is much like a shoe size, in the fact that such a measurement is unique from one individual to the next, and must be compensated for in order to achieve correct fitment.
Why is Draw Length Important?
The use of the proper form is the single biggest factor that influences an archer’s accuracy.
One of the most significant factors pertaining to proper form is the ability to anchor your shot consistently. This is where draw length plays an enormous role in overall accuracy.
If your bow’s draw length is set incorrectly, your ability to properly anchor your shot will almost certainly be negatively impacted.
As a result, your overall accuracy and consistency are likely to suffer. In short, you will never be as accurate with a poorly set or misconfigured draw length adjustment, as you could be if everything was to be set properly.
The reason that an incorrect draw length and anchor point negatively impacts accuracy is quite simple.
When at full draw, an archer’s arms should be at a 90-degree angle to their body. Your body should essentially be configured to a “T” shape between your torso and arms.
When shooting a bow with an improperly adjusted draw length, this is nearly impossible to accomplish.
As a result, under-draw or overdraw scenarios can present themselves. Both of these scenarios are detrimental to the overall form and can lead to immense difficulty when attempting to group arrows with consistency.
If a bow’s draw length is set at too great of a length for a particular archer, overdraw can be a concern. When draw length is properly set, a bow will cam over into the valley, reach full draw, and stop at an archer’s approximate point of anchor.
When a draw length is set too long, the bow does not reach its back-stop before an archer’s draw reaches a point where they can no longer anchor alongside the face as needed.
This creates improper upper body geometry, which causes an archer’s back to bow and their chest to protrude. This can also lead to other issues outside of poor accuracy, such as forearm string slap.
The polar opposite of overdraw is underdraw.
When a bow’s draw length is too short for the archer who will be firing it, an underdraw condition can be presented. When this occurs, the bow in question will cam over and reach its backstop far before actually reaching an archer’s point of anchor.
Instead of being able to keep your body in a perfect “T” formation, your back will be hunched over and your shoulders drawn forward at the time of releasing an arrow.
Because no true anchor point can be reached, accuracy typically nosedives when dealing with an underdraw scenario.
Measuring Draw Length
Much like any form of measurement, several schools of thought exist regarding how best to obtain your proper draw length value. Though these varying methods differ slightly in technique, they all still produce nearly identical figures when their steps are accurately followed.
The following are some of the most popular ways of determining your correct draw length.
One of the most popular ways of determining draw length is with the use of wingspan measurements.
This method is quick, simple, and efficient. All you need is an assistant, tape measure, and a calculator.
To begin taking wingspan measurements, stand with your back as straight as possible, and extend your arms outward to each side.
You will need to ensure that your arms are level with one another, and parallel to the floor. When this can be verified, it will be time to take the necessary measurement.
Have an assistant carefully measure the distance from the furthest fingertip on one hand, to that on the opposite side. Make sure that the measuring tape is pulled tight, and that no dangling free-play exists. Have your assistant record the figure that they observed in inches.
You will now divide the predetermined measurement by 2.5.
This will provide you with an accurate draw length figure to which your bow should be adjusted to accommodate.
Once any actual adjustments have been made, it is always advisable to double-check the unit’s fit and feel to ensure satisfactory results.
Sternum Midline Measurements (Button to Base Method)
Another viable way to determine an archer’s correct draw length is by way of sternum midline measurements.
This method of measuring draw length is perhaps the simplest of all. However, the sternum midline method of measurement tends to be somewhat less accurate in nature and is intended to provide more of a ballpark figure than anything.
Using this method, you will stand upright, with your bow arm (the arm which grips the bow) extended outward in a manner that places it parallel with the floor.
You will then use a tape measure to record the distance from the center-line of your sternum, to the base of your wrist on the arm that is extended.
The number in inches which is recorded will be your personal draw length.
It might also be helpful to relax your arm for a duration of time, then remeasure once more, in a bid to gain consistency.
Because this method tends to be somewhat less precise than other methods of measurement, double-checking your figures once more can add some level of uniformity to the process.
Yet another way of measuring draw length, is with the use of a specialized measuring arrow. These arrows can be found at nearly any archery pro-shop and can be purchased via the internet as well.
These specialty arrows are marked with varying length designations along their shaft. These designations are then used to take stock of an archer’s draw length when readying for the shot.
Therefore, nothing more is needed when using this method of measurement, other than your bow, a measurement arrow, and an assistant.
To complete this process, simply nock a specialty measurement arrow onto the bow string of the bow you wish to set up.
Now have an assistant watch as you slowly draw back your bow until reaching a comfortable anchor point.
Once anchored, your assistant will notate the bow’s measurement that is displayed on the arrow, at the exact location where it intersects the riser.
It is also important to remember that your form must be as it would when actually shooting while measuring your draw length in this manner. Doing so ensures that all measurements are correct and concise.
Draw Length Case Study
When measuring my draw length, I personally choose to use the above-mentioned wingspan measurement method.
I feel this method to be highly accurate and was taught this way of measuring draw length by an archery pro-shop owner in my area who has over 30 years of industry experience.
When setting up my latest compound bow, I stood in an upright manner, with my arms outstretched. In doing so, I made sure that my arms were parallel with the floor at all times, as this avoids any discrepancies. I then had an assistant measure my wingspan from fingertip to fingertip.
This revealed a wingspan measurement of 70 inches. I then divided this number by 2.5, which provided me with an overall draw length measurement of 28 inches.
This is a process that I have repeated several times throughout the years, as I make a habit out of double-checking such values of importance every time I set up a new bow that has been purchased.
Every time that I have measured my draw length in this manner, the results have been spot-on.
I simply set my new bow’s draw length to that which I have figured, draw back, and anchor without any issue whatsoever.
In my opinion, this has served as consistent proof that the wingspan method is a highly accurate means of measuring draw length.
Bow Considerations For Draw Length
If you are new to archery, it is important to take your probable draw length into consideration when choosing a bow to purchase.
While the bulk of bows today feature draw length ranges that are suitable for most adults of average height, those that are shorter or taller in stature can find it to be slightly more difficult to locate a bow that caters to their needs.
Since draw length is largely a product of height and wingspan, those that are under 5’ in height, or over 6’4 in height, will likely find their draw lengths teetering on the outer extremes of what is offered by a number of standard compound bows on the market.
Those who are under 5’ tall, are likely to have draw lengths of 23” or less, while those over 6’4 often have draw lengths that exceed 32”.
This in no way excludes these individuals from locating an excellent bow that suits their needs. However, one must do their homework to ensure that they are not purchasing a bow that lacks the range of adjustability to accommodate them.
Luckily, there are a substantial number of highly adjustable bows available on today’s market, that virtually eliminate these sizing issues.
The Draw Length Equation
Although it might at first seem intimidating, the process of measuring your personal draw length is no more difficult than you make it. By employing any of the three methods described above, you can record your draw length in a matter of only a few minutes.
The method that you choose to conduct this process is largely a matter of personal preference. However, it is important that you carefully follow the necessary steps to any process that is chosen.
This will ensure accuracy and spare you from being forced to make multiple fine-tune adjustments in a bid to compensate for any missteps or errors along the way.