how to measure compound bow string length

Complete Guide to Measuring Compound Bow String Length

Compound bows are a popular choice among archers due to their precision, power, and reliability. Unlike traditional recurve bows, compound bows utilize a levering system of cables and pulleys that provides a “let-off” effect, making it easier to hold the bow at full draw.

This advanced technology requires proper maintenance and care, including ensuring the bowstring is the optimal length. Even small deviations in string length can negatively impact the bow’s performance and your accuracy as an archer.

In this comprehensive guide, we’ll walk through how to measure compound bow string length the importance of measuring your compound bow’s string length, the necessary tools, and step-by-step instructions for getting precise measurements using different methods.

With the ability to accurately determine your string length, you can fine-tune your bow, troubleshoot issues, and ensure you’re getting the best performance possible each time you draw back and release.

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Importance of Knowing Your String Length Of Compound Bow

The specific string length affects the poundage and draw length of your compound bow. An improper string length can make your bow difficult to draw smoothly, uncomfortable to shoot, and less powerful.

It also introduces inconsistencies that ruin your accuracy. Here are some key reasons why getting the string length right matters:

Affects draw weight and draw length – With a shorter string, the bow’s weight feels heavier. A longer string makes it feel lighter. The draw length also changes.

Crucial for replacing strings or upgrades – You need to know the precise measurement when installing a new string.

Safety issues – A bow that’s too easy or hard to draw due to string length can lead to potential injury.

Fine-tuning for competition – Serious archers rely on dialed-in string lengths to optimize performance.

Maintains cam synchronization – The string and cables work together, so improper string length throws everything out of whack.

Regularly measuring your string length allows you to identify issues before they become major problems. Even high-quality bowstrings stretch over time, slowly increasing the length. It’s recommended to verify your measurements every few months or several hundred shots.

Tools You’ll Need to Measure Compound Bow String Length

To accurately measure your compound bow’s string length, you’ll need the following tools:

Measuring tape – A steel or cloth tape measure marked in inches or centimeters. Get one at least 60 inches/150 cm long.

Calipers – Precision calipers ensure accurate measurements.

Flat workbench or sturdy table – Provides an even surface for measuring.

Pencil or chalk – To mark the string for consistent measurement points.

Notebook or app – Record your measurements for future reference.

Unstringing tool – If measuring an unstrung bow, you’ll need a bow press or relaxing tool.

For the most precise measurements, use multiple tools like a tape measure in conjunction with calipers. This allows for verifying accuracy. Also, ensure your work area is as flat and stable as possible.

Method 1: Using a Measuring Tape

The most straightforward way to measure your compound bow’s string length is by using a measuring tape:

  1. Extend the string out to its full length. Have a partner hold each end or use a bow vise/jig.
  2. Determine the sections of string to measure between. Most bowstrings have end loops that fit over the cams or pulleys. You’ll want to measure from the bottom of one loop to the bottom of the loop on the opposite end.
  3. Carefully line up the tape end at one point. Stretch the tape tightly across to the opposite mark.
  4. Read the measurement and record it. Double-check for accuracy.
  5. If needed, calculate the AMO (Archery Manufacturers Organization) standard length. Simply add 3 3/4 inches to your measurement to find the AMO length.

The tape method provides a quick overall length measurement. For greater precision, move on to other techniques.

Method 2: Using a String Jig

A bowstring jig securely holds your string taut for easy, accurate measurements. To use one:

  1. Mount the string in the jig as directed. Most jigs have prongs or end caps the string loops fit over.
  2. Pull the string tight in the jig so there is no slack. Secure in place.
  3. Use measuring tape lined up precisely from end to end. Measure the same marked areas on the loops or ends.
  4. You can also use calipers to verify measurements across multiple points along the string.
  5. Take notes and check for consistency. Double-check the string for slack before re-measuring.

A quality string jig takes the hassle out of positioning the string and allows for easy repeat measurements.

Method 3: Measuring Without Removing the String

For a quick check without unwinding the string, use precision calipers:

  1. Identify where to measure between on each cam/pulley. Mark these spots.
  2. With the bow at rest, carefully measure between the marks using the calipers.
  3. To avoid introducing twists, be gentle and move smoothly as you extend the calipers.
  4. Repeat several times for consistency.
  5. Compare your measurements to your bow’s specs to identify any length issues.

This method won’t be extremely precise but provides a quick way to spot-check for major length problems before unstringing. It also avoids manipulating the string.

Common Mistakes to Avoid Measuring Compound Bow String Length

When measuring your compound bow string, there are some common mistakes that will affect your accuracy:

  1. Measuring from the wrong points on the string.
  2. Introducing extra slack or twist in the string.
  3. Assuming manufacturer specs are correct.
  4. Measuring against an uneven surface.
  5. Inconsistent tape pressure and alignment.
  6. Not accounting for serving thickness if present.
  7. Recording numbers incorrectly.

By being aware of these potential errors, you can take steps to get consistently reliable string length measurements.

Tips for Precise Measurement For Measure Compound Bow String Length

To achieve the most accurate and precise measurements of your compound bow string length:

Verify using multiple methods – Cross-check tape, jig, and caliper readings.

Always use a flat, sturdy surface – Avoid soft, uneven, or angled surfaces.

Watch for fraying or serving separation – This can impact measurement points.

Take measurements from a fully relaxed bow – No draw tension should be present.

Evaluate measurements over the whole string length – Look for inconsistencies.

Consider having a second set of eyes verify your process and readings.

Seek professional help from a bow technician if you need assistance.

Putting in the extra care will ensure you know exactly how long your bowstring is for tuning and replacement purposes.

Frequently Asked Questions about Compound Bow String Length

Some common questions about properly measuring compound bow strings include:

Can I use the same methods for recurve bows?

Yes, although the end loops differ on recurves, so your measurement points will change. The principles for measuring string length are largely the same between compound and recurve bows.

How often should I measure my bowstring?

Check the length every few months or several hundred shots at a minimum. Look for any major deviations from previous measurements.

Is it necessary to replace the string if the length varies from the standard?

Not always. You may be able to twist or untwist the strands to get back to the proper length. Major length changes mean the material is stretched out, which can lead to decreased performance and inconsistent shooting.


Accurately measuring your compound bow’s string length is crucial for performance. With the right tools and techniques, you can easily keep track of when the length changes over time. Just avoid common mistakes like introducing slack, measuring incorrectly, and recording errors. Verifying your measurements using multiple methods will ensure precision.

Knowing your bow’s optimal string length allows proper maintenance, troubleshooting of issues, and fine-tuning for improved shooting consistency.

Take time to regularly measure using a tape, jig, and calipers. With this complete guide, you now have the essential steps to measure your compound bow’s string like an expert.

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