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AMO length? Here’s What You Need To Know

As an archer, it is important to know everything about your bow even the smallest of standards such as the AMO length and what it means.

So what is AMO length?

AMO length is a standard measurement of bow length that is designated to be three inches longer than the bowstring. It usually applies to Recurve Bows and other “conventional bows”. For example: If your bow has an AMO length of 60″, the length of your bowstring, and the actual length of your bow when strung, will be 57″.

I am an archery enthusiast and as I learned more about my compound bow and other bows associated with AMO length, I started to hear all these terms that I didn’t quite understand.

I wanted to break it down for you…because once you know what these terms mean it will make life so much simpler.

Let’s start with the very beginning!

What is AMO?

AMO stands for Archery Manufacturers Organization. It was marginally created to be a set of standards for bows just like the bow length.

Bow designers are all over the world so there needed to be a set of standards and rules that designers followed that way it made shopping for bows easier for consumers.

Manufacturers will now have AMO measurements on the box or container of your bow to give you the standards that would fit your bow.

After awhile the Archery Manufacturers Organization became much more than just a set of standards. It became a community. Since then, they have changed their name to the Archery Trade Association.

The Archery Trade Association still holds their high standards for bow and bow designers but they give a community for all archers to go to. From classes to lobbying for archers.

They want to preserve and grow this amazing sport all around the world. You can find more amazing info at their website.

Now that you know a little bit of the history and hopefully the importance of what AMO stands; let’s dive in to the AMO length and what it exactly means.

AMO Length

AMO length is going to be somewhere on the container your bow came in or on your bow. It is going to include the bow length designation and the bow weigh category.

draw weight marking
60″ recurve bow with a 40 lb draw weight.

Example: AMO 60″, 40 lbs.

The picture below explains that as well but this is the AMO’s conventional bow string tension chart they follow when they are setting up these measurements. (As you can see, they are very accurate)

16 STRAND 60 AMO LENGTH RECURVE BOW STRING ACTUAL LENGTH STRING ...
Source: AMO Standards, 1987 (archerytalk.com)

Let’s stick with the example AMO 60″, 40 lbs.

When you see the AMO 60″ (this is the AMO length) you want to subtract 3.

60 – 3 = 57 (You subtract 3 for recurve bows…compound bows are a little more complicated)

69″ is going to be the bow length nock-to-nock when the bow is strung.

But listen..I hear all the time people say they can do this easy math and know what their bow length is.

But that is NOT TRUE!

This is the string length.

Why do they call it bow length….I have no clue. But I want to make this very clear.

AMO LENGTH HAS DOES NOT MEAN “BOW LENGTH.”

There I said it…it only has to do with string length. I have talked and had deep conversations with many string designers for bows and that is all it is. It will help you get your string length.

In other words, when you need to replace your bowstring, this is what you will use the get the string length. It is that simpler. Your welcome!

This image is such a good representation of what ideal vs. reality. AMO length vs. the actual length.

Whenever you talk to an archer they always tell you their bow length in inches. That is because the AMO has always used that metric to state the AMO length.

So now you know what the AMO stands for and how you can use it in the future to replace your string.

But what if you want to manually measure your bowstring to make sure. Good Question!

Manually Measure Your Bowstring

Maybe you bought your bow used and the AMO or label is missing on the bow and now you are left to figure out the bowstring length yourself.

Don’t worry! Its really easy.

Measuring Bowstring Length for Recurve Bows

To find the correct bowstring length on a recurve bow, all you need is a tape measure. I am going to use a recurve bow in this example.

You are going to take the tape and measure along the curve of the bow limbs from the string groove to string groove. This is going to be your string length.

Another way is to measure your bow from tip to tip to find the AMO length and then subtract accordingly to the type of bow you are using.

When you are measuring, make sure to measure across the face of the bow limbs and not to curve into the handle.

Now, when it comes to measuring a compound bow, this part gets a little trickier.

You are going to need a marker to mark the bow and a bow press to hold the bow.

AMO length standards suggests that a compound string length needs to be determined by applying 100 lbs. of tension and then you have to measure from the outside of the pin to the outside of the other pin with your string.

Most manufactures have a string tensioner which is a type of machine used to make this process a whole lot easier.

But since we are doing it ourselves, you want to put the bow in a bow press and take a piece of string and make a loop. Place it on the peg found on the cam and then wrap it around the cams. Then bring the string to the other peg on the other side of the bow.

Go ahead and hold the cams so that they look similar to when the bow is being strung. You can adjust the brace height to ensure a good feel and look for how the bow will look once its fully strung.

Then you are going to take the marker and mark the string at the peg on the opposite side of the loop. And then you can measure the length of the string from the loop to the mark. This will be your proper length needed for you compound bow.

This process is going to be a lot easier if you have an extra pair of hands.

I personally would go to a professional bow stringer or you local archer pro shop to help with a compound bow just to make sure it’s accurate.

Conclusion

I think a lot of newer archers (like when I first started) get very intimidated when they see all these measurements and strange references they have never heard of such as AMO.

And I have gone to several archery pro shops and professionals to learn more about my bow and I never heard AMO but only a handful of times.

But it is good to be knowledgeable and to know every aspect of your bow even the string length. You can take your bow to a professional and they can do it for you and there won’t be a problem.

But to know what AMO means and how to find your string length can be very helpful and make you more aware of your bow and increase your skills.

I would also recommend checking out the Archery Trade Association. Knowing more about this association and the history, gives you the appreciation of what they do for all archers.

Related Questions

How do you determine your true draw length? You can measure your true draw length by marking the arrow at the grip area. The distance from the grip area to the nock that meets the string is your true draw length.

How do you measure amp draw length? The amp draw length is determined by measuring where the nock point is to the point that is the deepest part of your grip. This is where the arrow will cross the riser You can also use a bow square to figure this out as well.

Can arrows be too long for a bow? Yes and no. This depends if you have the right length arrow for your stature. But Yes because the longer the arrow the weaker the spine will be.