How To Measure A Bows Draw Length. Why It Is Important For Accuracy.

How to measure draw length of a compound bow.

Having your compound bow’s draw length set at the correct length is vital for accuracy.

So knowing how to measure a bows draw length is important in this step.

We will get into the how to measure the draw length for the bow straight away. Then get into the details about how and why, further on below in the article.

(Please read this extra information, as it explains the difference between the archers draw length and the bows draw length. Which is important to know the difference.)

 

ATA (AMO) method. How to measure the draw length of a bow. 

We will use the ATA method. The bows draw length is measured from the arrow nock grove point on the string, when the bow is drawn back to the pivot point of the grip, plus 1 ¾”.

How to measure a bows draw length.

The pivot point of the bow is the narrowest part of the bow grip. (This on some bows will align up with the berger hole, or plunger button hole. But not always.)

Now we have the big picture on measuring the bows draw length, we will go through it step by step on how to do it.

1. Below image. We will put some tape on the riser, above the pivot point of the handle. (Painters tape is ideal, as it shouldn’t mark the bows riser.)

Measuring brace height on bow

 

2. As above photo. Use a tape measure, or bow square (“T” square.) to measure the bows brace height. The brace height is measured from the bow string (Not drawn.) to the pivot point of the handle.

3. Below image. The brace height is then transferred and marked on the tape. Use a Sharpie or pen to mark on the tape.

How to measure draw length of bow.

4. Mark an arrow with a Sharpie with inch and half inch increments. You might put quarter increments as well on it.

Or put the painters tape on the arrow and mark the increments. (The measurement is taken from the arrow nock groove.)

Measure arrow length

5.  Below photo. Draw the arrow back. Have a friend take note of where the mark lines up with the arrow. (Or video tape the riser / arrow rest area.)

When you draw the arrow back, make sure you do it safely with a target in front and a large safe backstop. Stand on level ground and make sure you are aiming level, not aiming up or down.

Compound bow, draw length measurement.

6. Once you have a measurement, add 1 ¾ inches to the measurement. This is the bows draw length setup.

As an example of how to measure a bows draw length. If you draw the arrow back, and it lines with the mark on the tape at 26 ¼ inches. Then add 1 ¾ inches to the measurement. 26 ¼ “ + 1 ¾ “ = 28 inches.

The 28 inches is this compounds bow draw length set up.

Measure compound bows draw length.

 

Extra information on how to measure a bows draw length.

Unlike a recurve bow, or longbow that you can draw most lengths. A compound bow is set at a specific range, or the bows draw length.

With a lot of compound bows you can change this range, buy you need to know what is set up at.

Please don’t confuse your draw length, with what the compound bows draw length is set at.

As an example, your perfect draw length might be 28 inches. While the compound bow might be set at 29 inches draw length. You will not get the best accuracy shooting a compound bow that is either too long, or too short for you.

This is a very important point. The compound bows draw length set up, should suit your draw length. Not the other way around. The bow should suit you, not you trying to match the bow.

If you are a beginner to archery, there are several ways to find out your rough draw length. Visit,  How To Figure Out Your Draw Length  for more information.

Once you know your draw length you can then adjust the compound bow to suit you.

Here is some more information about how vital the Correct Draw Length is.

How to measure arrow length?

The arrow is measured from the knock groove to the end of the shaft. The arrow point and insert is not measured, as per below picture.

How to measure an arrow.

For measuring an arrow the correct way, visit  How To Measure An Arrow  for more information.

 

Other ways on how to find out the draw length of a bow.

So how do you find what draw length the compound bow is, without using the above method?

Most compound bows are set from the factory at 29 inches. (Some compounds you can’t adjust the draw length. They have set cams and lengths and are generally the speed bows. But the majority you can change.)

Now 29 inches is generally too long for most archers. Unless you are taller side, or over a medium height. So it might need adjusting.

You can request the archery pro shop to change it, but you have to know your ideal draw length first.

So getting back to the question, how do you find what draw length the compound bow is set at?

A lot of compound bow manufactures will have some instructions on how to change it. Some bows have interchangeable modules on the cams, or settings.

The instructions and settings / modules might state something like; module B = 27 inches, module C = 28 inches and module D = 29 inches.

So in this example if you had module D, then the bows draw length would be set at 29 inches.

But sometimes the instructions / settings, can be confusing. So we have to physically check the bows draw setting.

 

More information about the ATA (AMO) draw length standard.  Measuring the bows draw length.

There are two methods of measuring the bows draw length, the ATA method (Which is from the knocking point on the drawn string, to the pivot point of the grip plus 1 .75”.) The other method is called the true draw method.

ATA stands for, Archery Trade Association (Previously it was called AMO, or AMMO. Which was the “Archery Manufacturers & Merchants Organization”. This helps have set measuring standards and guidelines across the archery manufactures and archery in general.)

The ATA method, is the most common method and what most archery companies use for measuring the compound bows draw length.

Compound bows, recurves and longbows can all be measured using the ATA method.

This is the method we used for the above step by step method. Here it is again. When an arrow is drawn back, the arrow nock from the string groove is measured to the pivot point of the grip, plus 1 ¾ inches.

The ATA bow draw length measurement was initially designed so that the end of the arrow would be about level with the back of the riser. (The part of the riser facing you is the belly.)

(A rough guide for traditional bows was if you used broadheads, you would cut your arrows about an inch longer past the riser. So the back of the broadhead would not nick your hand.)

 

 

Three archery measurements you should know.

There are three basic measurements in archery, the arrows length and the archers draw length.

Which should not be confused with a compound bows draw length measurement, that it is set at.

(A fourth measurement is the length of a bow. Or for a compound bow, you measure from the axle to axle.)

 

 

True draw length method.

The other method for measuring the bows draw length is, called the true draw length. This is measured from the nock point on string when the bow is drawn back to the pivot point of the grip.  (Note – The 1 ¾” is not added.)

The true draw length method is not used much today. But some European traditional bow makers, or bowyers might still use it.

 

Tips for measuring the bows set up.

Make sure you have a large backstop and it is safe when you draw the bow and arrow back.

Stand on flat level ground and makes sure your target is level with your bow arm.

If you are not level and you are shooting up or down hill, your form may look or feel awkward.

Have the bows draw weight poundage set low, so you are not struggling with the weight.

Never dry fire the bow. (Release the bow without an arrow.) As the energy can damage the limbs or bowstring.

 

Archery FAQ. (Frequently Asked Questions.)

 

Why is knowing the compound bows draw length important?

A compound bow will draw back only a specific distance before it stops and hits the wall.

When you draw back the compound, the poundage peaks rapidly, as the cams or wheels turnover.

It then goes to the drop off, or let of phase. This is where you are holding less poundage bows draw weight. This is called the valley.

After the valley, you can’t draw a compound back any more and you hit a mechanical stop called the wall.

Because of this mechanical stop, it is important to find out if the compound bows set up, will match your draw length.

 

What happens if I don’t adjust the compound bows draw length?

If you don’t match the compound bows draw length setting to suit your draw length, your accuracy can be poor.

If the bows draw length is too long for you, you will lean back. Your posture won’t be like a “T” and your alignment will be off, thus effecting your accuracy.

Also with a draw length that is too long draw, the bow string might contact your chest or face. Causing interference and a poor release, thus interfering with accuracy.

High and low shots on target may occur as you are leaning back.

For bowhunters using a too long of draw length, the bowstring may contact with their 3D leaf suit or face veil, causing a poor shot as well.

If the compound bow draw length is set too short, it can be harder to use your back muscles and bone alignment, and your arm muscles may fatigue earlier. Also decreasing accuracy.

 

My bow is set at 28 inches, yet it measures 28 ¼ inches. Why is this?

A lot of bows I have measured are not exactly what the specs state, sometimes this is due to cables and string stretching. (Creeping.)

Another reason is the manufacturing process may vary from bow to bow. Especially if you have a range of different draw lengths, bow draw weights, from the one model bow, etc.

Also when you wind up or down the poundage, this changes the angle of your limbs and can affect the brace height and your draw length a little bit.

One theory I have heard from people, is: Some manufactures intentionally make the bows draw length longer. (I don’t think theory holds weight and is unintentional.)

This would make IBO speeds faster.  As an example, the draw length for IBO is 30 inch. Having a slighter longer draw length then gets more power stroke, hence faster arrow speed.  This looks better for feet per second speed. While a 1/8 of an inch might not sound much, when you are talking selling bows (And speed does sell bows.) every foot per second of speed can mean a lot of sales to a bow company.

 

Does a d loop add length to your bows draw length?

No. The technical draw length of a bow is from the string on the arrow knock, drawn back, to the pivot point of the grip plus 1 ¾ inches.

So the d loop changes where you anchor, but not the compound bows draw length set up.

Your ideal draw length is still the same as well, but you might anchor back more with a d loop on.

 

Does an arrow rest affect my draw length or the bows?

No, the arrow rest doesn’t affect your draw length, or the bows measurement.

 

What about draw lengths for recurves and longbows?

Recurve bow draw length.

The bows draw length measurements still apply to longbows and recurve bows as the ATA method.

However for recurves and longbows, the draw length set up is not fixed, like in a compound bow.

You can draw a recurve and longbow back a wide range, this will of course depend on the length and design of the recurve or longbow.  (An example could be from say you can draw it from 8 inches to 31 inches.)

Some bows will stack. This means it will be harder to draw back a longer way, then what the bow was designed for.

The ATA measurement is handy though, for finding the draw weight for recurves and longbows. (Generally at 28” draw length.)

This can vary at fair bit, but for every inch of draw length, the draw weight of the bow might go up 2 lbs. (This might be one pound or three pounds, but just a rough guideline.)

Recurve bow draw length and poundage.

An example could be, for the recurve bow above. The manufacturer states the bow is 40 lbs draw weight at 28 inches. (Indicated in blue.) If you draw the bow to 27 inches. (Indicated in yellow.) it might only be 38 lbs in draw weight.

If you draw the bow to 26 inches, it could be 36 lbs of draw weight. (Indicated in green.)

Or another example if you draw past 28 inches and get to 29 inches, then you might be holding 42 lbs of draw weight.

 

Conclusion – How to measure a bows draw length.

Selecting the correct bow, which matches your draw length is important for getting the best accuracy. So we should know how to measure a bows draw length correctly.

Remember to match the bow to you, not the other way around.