Bow String Length Calculator

Your expert tool for finding the perfect string length for your traditional bow.

Formula Used: The actual string length is estimated by subtracting a standard value from the bow’s AMO length. Generally, this is 4 inches for recurve bows and 3 inches for longbows. This is a starting point for proper tuning.

Common Bow String Lengths

AMO Bow Length	Recurve String Length (Actual)	Longbow String Length (Actual)
60″	56″	57″
62″	58″	59″
64″	60″	61″
66″	62″	63″
68″	64″	65″
70″	66″	67″

This table provides quick reference for recommended actual string lengths based on common AMO bow lengths. Use our bow string length calculator for specific values.

Understanding the Bow String Length Calculator

Welcome to the ultimate guide and tool for every traditional archer. The bow string length calculator is an essential utility designed to eliminate the guesswork in finding the perfect string for your bow. A correctly sized string is paramount for safety, accuracy, and the longevity of your equipment. This article provides not only a powerful calculator but also a deep dive into everything you need to know about bow string lengths.

What is a Bow String Length Calculator?

A bow string length calculator is a tool that determines the *actual* physical length of a string you should purchase or make for your bow based on its AMO (Archery Manufacturers and Merchants Organization) designated length. AMO length is the industry standard for measuring bows, but it does not equal the actual string length. The string is always shorter because it sits straight between the bow tips, while the bow’s length is measured along its curves.

Who Should Use This Calculator?

This calculator is indispensable for traditional archers, including those who shoot recurve bows and longbows. Whether you are buying a pre-made string or crafting your own, using a reliable bow string length calculator ensures you start with the correct baseline length for optimal performance. It’s especially useful for beginners who may not be familiar with the “rules of thumb” and for experienced archers looking for a quick and accurate calculation. Compound bow archers should not use this tool, as their strings and cables are highly specific and must match manufacturer specifications precisely.

Common Misconceptions

A primary misconception is that a 68-inch bow needs a 68-inch string. This is incorrect and could lead to poor performance and an improper brace height. Another common error is using the same formula for all bow types. As our bow string length calculator demonstrates, recurves and longbows require different length reductions. Finally, many believe the calculated length is the final word, but it is actually a starting point. Fine-tuning by twisting or untwisting the string to adjust brace height is often necessary.

Bow String Length Formula and Mathematical Explanation

The mathematics behind the bow string length calculator are straightforward but critical. It’s based on an industry-standard formula that provides a reliable starting point for fitting a string to a bow.

The general formulas are:

• For Recurve Bows: Actual String Length = AMO Bow Length - 4 inches
• For Longbows: Actual String Length = AMO Bow Length - 3 inches

The difference in reduction (4 inches vs. 3 inches) accounts for the geometry of each bow type. Recurve bows have tips that curve away from the archer, requiring a relatively shorter string to achieve the proper brace height compared to the straighter profile of a longbow. This calculator automates this selection for you.

Variables Table

Variable	Meaning	Unit	Typical Range
AMO Bow Length	The standardized length of the bow, measured along the limbs.	Inches	48″ – 72″
Bow Type	The style of traditional bow (Recurve or Longbow).	N/A	Recurve, Longbow
Length Reduction	The amount subtracted from AMO length to find actual string length.	Inches	3″ or 4″
Actual String Length	The physical, end-to-end measurement of the bow string.	Inches	44″ – 69″

Practical Examples (Real-World Use Cases)

Example 1: Standard 68″ Recurve Bow

• Inputs: AMO Bow Length = 68″, Bow Type = Recurve.
• Calculation: 68″ – 4″ = 64″.
• Output: The bow string length calculator recommends an actual string length of 64 inches. This would be the correct size to order. The archer can then install it and begin the tuning process by checking the brace height, which for a 68″ bow should be around 8″ to 9″.

Example 2: Common 70″ Longbow

• Inputs: AMO Bow Length = 70″, Bow Type = Longbow.
• Calculation: 70″ – 3″ = 67″.
• Output: The calculator suggests an actual string length of 67 inches. For most longbows, this will result in a brace height in the recommended range of 6″ to 7″. The archer should then string the bow and measure the brace height to confirm.

How to Use This Bow String Length Calculator

Using our bow string length calculator is simple and intuitive. Follow these steps to get an accurate result in seconds.

1. Enter AMO Bow Length: Find the AMO length of your bow. It’s usually printed on the lower limb. Enter this value in inches into the first input field.
2. Select Bow Type: Choose either “Recurve Bow” or “Longbow” from the dropdown menu. This is a critical step, as the formula changes based on your selection.
3. Review Your Results: The calculator will instantly display the recommended “Actual String Length.” This is the primary result. You will also see intermediate values like the standard reduction applied and the estimated brace height range for your bow size.
4. Copy or Reset: You can use the “Copy Results” button to save the information for your records or when shopping for a string. The “Reset” button restores the default values.

Remember, the result from this bow string length calculator is your starting point. Always check your bow manufacturer’s specific recommendations if available. Learn more about {related_keywords} for advanced tuning.

Key Factors That Affect Bow String Length Results

While the bow string length calculator provides an excellent baseline, several factors can influence the final string length and bow tuning. Understanding these is key to achieving peak performance.

1. String Material: Modern strings are made from materials like Dacron, Fast Flight, and other synthetics. Materials with less stretch (like Fast Flight) may require a slightly different length or more twists to achieve the desired brace height compared to stretchier materials like Dacron (B-55).
2. Brace Height: This is the distance from the deepest part of the grip to the string when the bow is strung. A shorter string increases brace height; a longer string decreases it. Finding the “sweet spot” for your brace height is crucial for a quiet, forgiving shot, and our bow string length calculator gets you into the right ballpark.
3. Number of Twists: A bow string’s length can be shortened by adding twists. This is the primary method for fine-tuning brace height. A Flemish twist string offers more adjustability than an endless loop string.
4. Bow Geometry: Highly reflexed or deflexed bow designs might deviate from the standard formula. Always default to the manufacturer’s recommendation for such bows. Using a generic bow string length calculator might not be accurate for extreme designs.
5. String Creep/Stretch: New strings, especially those made of Dacron, will stretch over the first hundred shots. You will likely need to add twists to the string to bring the brace height back into the optimal range. This is a normal part of the break-in process.
6. Archer’s Feel and Sound: The ultimate test is how the bow shoots. An incorrect brace height (stemming from an incorrect string length) can lead to a loud, inefficient shot or excessive string slap on the wrist. Adjusting the length by twisting the string until the bow feels smooth and sounds quiet is the final step. A properly configured bow, guided by a bow string length calculator, makes a huge difference. For more on how form affects performance, see our guide on {related_keywords}.

Frequently Asked Questions (FAQ)

1. What is AMO and why is it important?

AMO stands for the Archery Manufacturers and Merchants Organization. They created standards to ensure consistency in equipment, including bow length. AMO length is measured along the curve of the unstrung bow’s limbs from string groove to string groove. It’s important because it creates a universal reference for tools like this bow string length calculator. Interested in standards? Read about {related_keywords}.

2. What happens if my bow string is too long?

A string that is too long will result in a low brace height. This can cause the string to slap against your armguard or wrist, make the bow louder, and reduce arrow velocity. It can also make the bow feel less stable at full draw.

3. What happens if my bow string is too short?

p>A string that is too short creates a high brace height. This can put excessive strain on the bow limbs, potentially leading to damage over time. It also reduces the power stroke of the bow, decreasing arrow speed and efficiency.

4. Can I use a longbow string on a recurve bow?

No, you should not. As the bow string length calculator shows, the required lengths are different. Using a longbow string (which would be too long) on a recurve would result in a very low brace height and poor performance.

5. How do I measure my existing string to get its length?

To measure an existing string, remove it from the bow. Hook one end loop over a nail or peg, apply light tension to pull it straight, and measure to the far end of the other loop. This gives you its “actual length.”

6. Why does the bow string length calculator have different rules for recurve and longbow?

The limb geometry is the reason. A recurve bow’s tips curve away from the archer, storing more energy and requiring a different string-to-bow-length ratio to achieve a stable brace height compared to the gentle curve of a longbow. For other archery calculations, check our {related_keywords}.

7. How many twists should I put in my new string?

A new Flemish twist string should have at least 15-20 twists to keep the bundles tight. From there, you can add or remove twists in small increments (2-3 at a time) to fine-tune your brace height until the bow shoots quietly and feels right. An endless loop string has less room for adjustment.

8. Does string material affect the length I need?

Yes, indirectly. Low-stretch materials like Fast Flight won’t creep as much as Dacron. You might start with the same length from a bow string length calculator, but a Dacron string will require more twisting over its life to maintain the correct brace height as it settles in. Our guide to {related_keywords} can help you choose.