Evertune Calculator

The ultimate tool for calculating guitar string tension to perfect your Evertune bridge setup.

String Tension Calculator

What is an Evertune Calculator?

An Evertune calculator is not a device that magically sets up your bridge. Instead, it’s an essential tool, specifically a guitar string tension calculator, designed for musicians who use the Evertune bridge system. This calculator helps you determine the exact pulling force (tension) a string will exert when tuned to a specific pitch on a particular scale length. Understanding this tension is the most critical factor in achieving a perfect Evertune bridge setup. The bridge works by balancing the string’s tension against an internal spring. If you know the tension, you can predict how the saddle will behave, making it much easier to dial in “Zone 2” – the sweet spot where your guitar stays perfectly in tune.

Many guitarists mistakenly believe the Evertune is a ‘set and forget’ system without understanding the physics behind it. The reality is that factors like guitar string tension are paramount. This Evertune calculator removes the guesswork, allowing you to make informed decisions about string gauges and tunings, ensuring your Evertune performs exactly as designed.

Evertune Calculator Formula and Mathematical Explanation

The core of this Evertune calculator is the industry-standard formula for calculating string tension. It combines three key variables: the string’s unit weight, the guitar’s scale length, and the target frequency (pitch).

The formula is as follows:

T = (UW * (2 * L * F)²) / 386.4

This equation provides the tension in pounds (lbs). Here is a step-by-step breakdown of how the calculation works:

1. (2 * L * F): This part calculates a value related to the wave speed on the string. It doubles the scale length and multiplies it by the frequency.
2. (…)²: This result is squared. Tension increases with the square of frequency and length, meaning small changes can have a large impact.
3. UW * …: The squared value is then multiplied by the string’s Unit Weight (its mass per inch). Heavier strings naturally create more tension.
4. … / 386.4: The final value is divided by a gravitational constant (386.4 in/s²) to convert the units correctly into pounds of force.

Variables Table

Variable	Meaning	Unit	Typical Range
T	Tension	Pounds (lbs)	8 – 28 lbs
UW	Unit Weight	Pounds per Inch (lb/in)	0.00001 – 0.00040
L	Scale Length	Inches (in)	24.75″ – 27″
F	Frequency	Hertz (Hz)	73 Hz (D2) – 330 Hz (E4)

Practical Examples (Real-World Use Cases)

Example 1: Fender Stratocaster in E Standard

A player wants to set up their Fender Stratocaster (25.5″ scale) with a standard .046 gauge low E string for E Standard tuning (E2). Using the Evertune calculator:

• Inputs:
  • Scale Length: 25.5″
  • String Gauge: .046″ (Unit Weight ≈ 0.00038216 lb/in)
  • Note: E2 (Frequency ≈ 82.41 Hz)
• Output:
  • Calculated Tension: ≈ 17.5 lbs

Interpretation: A tension of 17.5 lbs falls comfortably within the range of a standard Evertune saddle (typically 10-28 lbs). The player knows this setup is viable and can proceed with the mechanical Evertune bridge setup, confident the tension is correct.

Example 2: Gibson Les Paul in Drop D

Another player wants to use their Gibson Les Paul (24.75″ scale) for Drop D tuning. They want to calculate the tension for their 6th string, a .052 gauge, tuned down to D2.

• Inputs:
  • Scale Length: 24.75″
  • String Gauge: .052″ (Unit Weight ≈ 0.00049444 lb/in)
  • Note: D2 (Frequency ≈ 73.42 Hz)
• Output:
  • Calculated Tension: ≈ 19.4 lbs

Interpretation: Even with a heavier string and shorter scale, the tension is 19.4 lbs. This is a healthy value, ensuring the string isn’t too floppy and will work perfectly with the Evertune. This demonstrates how a shorter scale length reduces tension, a key factor in guitar playability.

How to Use This Evertune Calculator

Follow these simple steps to calculate string tension and optimize your Evertune bridge setup.

1. Enter Scale Length: Input your guitar’s scale length in inches. If you’re unsure, 25.5″ is common for Fender-style guitars and 24.75″ for Gibson-style guitars.
2. Select String Gauge: Choose the specific gauge of the string you are calculating from the dropdown menu.
3. Select Note/Pitch: Choose the note you intend to tune the string to.
4. Read the Results: The calculator will instantly display the primary result: the string’s tension in pounds. It also shows the intermediate values (Unit Weight and Frequency) used in the calculation.
5. Make Decisions: Use the calculated tension to decide if a string gauge is appropriate for your tuning. Too low (under 10 lbs) might feel floppy, while too high (over 28 lbs) may require a special high-tension Evertune saddle. Understanding this helps master your Evertune intonation and setup.

Key Factors That Affect Evertune Results

Several factors influence your string tension and, consequently, your Evertune calculator results and setup.

1. String Gauge

This is the most direct factor. A thicker string has more mass (higher unit weight), resulting in significantly higher tension at the same pitch and scale length.

2. Scale Length

The distance from the nut to the bridge saddle. A longer scale length requires more tension to bring a string up to the same pitch. This is why baritone guitars have such high tension.

3. Tuning (Pitch/Frequency)

Higher pitches require more tension. Tuning a string up from E to F, for example, increases its tension dramatically. This is why drop-tuning makes strings feel looser.

4. String Material

Different materials (e.g., nickel-plated steel, pure nickel, stainless steel) have different densities. This Evertune calculator is based on D’Addario’s popular nickel-wound strings, but results may vary slightly with other materials.

5. Core-to-Wrap Ratio

For wound strings, the ratio of the inner core wire’s thickness to the outer wrap wire’s thickness affects the unit weight and flexibility. This is a more advanced concept but influences the final tension value.

6. Bend Sensitivity Setting

While not part of the tension calculation, how you set the bend sensitivity on the Evertune itself determines how close you are to the “choke” point (where bends are disabled). A proper tension calculation ensures you have enough range to set this effectively. Proper setup is key to finding the Evertune Zone 2.

Frequently Asked Questions (FAQ)

1. What is Evertune’s “Zone 2”?

Zone 2 is the “sweet spot” where the Evertune bridge is active. In this zone, the tension from the string is perfectly balanced by the spring in the saddle. As a result, small changes in tension from temperature shifts or turning the tuning peg do not affect the pitch, keeping the string perfectly in tune.

2. Can I still bend strings with an Evertune?

Yes. By applying enough pressure to bend the string, you add enough tension to pull the saddle to the end of its travel range, causing the pitch to rise just like on a standard bridge. You can adjust how easily this happens via the bend sensitivity setting.

3. Why is my string tension important for an Evertune?

Evertune saddles are designed to operate within a specific tension range (e.g., 10-28 lbs for standard modules). If your string tension is too low or too high, the saddle may not be able to balance the force correctly, preventing you from entering Zone 2. This Evertune calculator helps you verify your setup is compatible.

4. Does this Evertune calculator work for 7-string or 8-string guitars?

Yes. The physics of string tension are the same regardless of the number of strings. Simply enter the scale length, gauge, and desired note for your 7th or 8th string to get an accurate tension reading. You may need a high-tension saddle for very heavy low strings.

5. How does string tension affect my guitar’s tone and feel?

Higher tension strings generally feel stiffer and sound brighter with a sharper attack. Lower tension strings feel “slinkier” and easier to bend, often with a warmer, fuller tone. Using an Evertune calculator helps you find a balance that feels and sounds right for you.

6. What if my calculated tension is outside the standard range?

If your tension is below ~10 lbs or above ~28 lbs, you may need a different saddle module. Evertune sells “Low Tension” and “High Tension” saddles to accommodate a very wide range of tunings and string gauges.

7. Why doesn’t this calculator consider action or intonation?

While action (string height) and intonation (string length adjustment) are crucial parts of a setup, they have a negligible effect on the string’s static tension compared to gauge, scale length, and pitch. This Evertune calculator focuses on the primary tension calculation, which is the first and most important step.

8. Is a higher tension number better?

Not necessarily. “Better” is subjective. Some players prefer the taught, responsive feel of high tension for aggressive rhythm playing. Others prefer the soft, buttery feel of low tension for lead playing and easy bending. The goal of this Evertune calculator is to help you achieve a consistent and comfortable feel across all strings.

Related Tools and Internal Resources

• Scale Length to Fret Spacing Calculator: A tool to calculate fret positions for any custom scale length.
• Complete Guide to Guitar String Gauges: An in-depth article explaining how string gauges affect tone, feel, and tuning stability.
• Step-by-Step Evertune Setup Guide: Our comprehensive walkthrough of setting up and intonating an Evertune bridge from start to finish.
• Understanding Guitar Intonation: Learn why intonation is critical for playing in tune across the entire fretboard.
• The Benefits of Balanced Tension String Sets: Explore how sets with matched tension across strings can improve your playing experience.
• How to Choose Strings for Drop Tuning: A guide dedicated to selecting the right gauges to avoid floppy strings in low tunings.