What is an Evertune Tension Calculator?
An Evertune Tension Calculator is a specialized online tool designed to help guitarists and luthiers determine the precise string tension for instruments equipped with an Evertune bridge system. Unlike traditional fixed bridges, the Evertune bridge maintains constant string tension, eliminating tuning instability and intonation issues. However, for the Evertune system to function optimally, each string must be tensioned within a specific "sweet spot" or "zone."
This calculator takes into account crucial factors like the instrument's scale length, the string's gauge (diameter), the desired musical note (tuning), and the string material to compute the resulting tension. By providing these inputs, users can ensure their Evertune setup delivers its promised performance, preventing strings from being too slack or too tight for the bridge mechanism.
Who Should Use It?
- Guitarists with Evertune: To fine-tune their string choices for optimal performance and feel.
- Luthiers & Guitar Techs: For precise setups and string recommendations.
- Musicians Experimenting with Tunings: To understand how different tunings and string gauges impact tension.
- Anyone curious about string mechanics: To gain a deeper understanding of how string properties affect sound and playability.
Common Misunderstandings (Including Unit Confusion)
A common misconception is that heavier gauge strings always mean higher tension. While generally true, scale length and tuning play equally significant roles. Many users also confuse string gauge with tension directly, but gauge is merely a measurement of diameter, which contributes to the string's unit weight, a key factor in the tension formula.
Unit confusion is also prevalent. String gauge can be expressed in "mils" (thousandths of an inch) or millimeters. Scale length can be in inches or millimeters. Tension is commonly measured in pounds (lbs), but kilograms (kg) or Newtons (N) are also used. This calculator allows you to select your preferred units for clarity and accurate calculations.
Evertune Tension Formula and Explanation
The calculation of string tension is rooted in fundamental physics principles, primarily derived from Mersenne's laws. The core formula used by this evertune tension calculator is a variation of the vibrating string formula, adapted for common guitar string units:
Tension (T) = (Unit Weight (UW) × (2 × Scale Length (L) × Frequency (F))^2) / gc
Let's break down each variable:
Variables for String Tension Calculation
| Variable |
Meaning |
Unit (Default) |
Typical Range |
| T |
Calculated Tension |
Pounds (lbs) |
8 - 25 lbs per string |
| UW |
Unit Weight of String |
lbs/inch |
0.00001 - 0.00015 lbs/inch |
| L |
Vibrating Scale Length |
Inches (in) |
24.75" - 27" |
| F |
Frequency of Target Note |
Hertz (Hz) |
60 Hz (low C) - 330 Hz (high E) |
| gc |
Gravitational Constant (for unit consistency) |
386.4 (lbs, inches, Hz) |
Constant |
The Unit Weight (UW) is further derived from the string's gauge (diameter) and its material density. Heavier gauges and denser materials result in a higher unit weight. The Frequency (F) is determined by the specific musical note you tune the string to. A higher note means a higher frequency. Finally, the Scale Length (L) is the distance from the nut to the bridge saddle, influencing how much string needs to vibrate to produce a given pitch. The Evertune bridge benefits from this precise calculation to ensure each string sits perfectly within its operating zone.
Practical Examples
Let's look at a couple of scenarios to illustrate how the evertune tension calculator works:
Example 1: Standard Tuning, Regular Scale
A guitarist wants to set up their 25.5-inch scale length guitar with standard Evertune tuning (E Standard, E2-E4) using a common 10-46 gauge set. Let's calculate the tension for the low E string (E2) using a 0.046" (46 mil) plain steel string.
- Inputs:
- Scale Length: 25.5 inches
- String Gauge: 46 mils (0.046 inches)
- Target Note: E2 (82.41 Hz)
- String Material: Plain Steel
- Calculation (simplified): The calculator processes these inputs, deriving the unit weight from gauge and material, then applies the tension formula.
- Results (approximate):
- Calculated Tension: ~17.5 lbs
- Frequency: 82.41 Hz
- Unit Weight: ~0.000085 lbs/inch
- Evertune Zone: Within Optimal Range (Optimal)
In this case, the 17.5 lbs tension for the low E string falls comfortably within the Evertune's optimal operating range (typically 10-18 lbs), indicating a good setup.
Example 2: Drop Tuning, Baritone Scale
Another guitarist uses a 27-inch baritone guitar and wants to tune to Drop C (C2) using a heavier string, say 0.060" (60 mil) nickel wound string.
- Inputs:
- Scale Length: 27.0 inches
- String Gauge: 60 mils (0.060 inches)
- Target Note: C2 (65.41 Hz)
- String Material: Nickel Wound
- Calculation (simplified): The calculator adjusts for the longer scale length and lower frequency.
- Results (approximate):
- Calculated Tension: ~16.2 lbs
- Frequency: 65.41 Hz
- Unit Weight: ~0.000143 lbs/inch
- Evertune Zone: Within Optimal Range (Optimal)
Even with a much lower tuning and heavier string, the longer scale length helps maintain tension within the Evertune's optimal zone, demonstrating the balance required for extended range instruments. If this result was too low (e.g., <10 lbs), the guitarist might consider an even heavier gauge string or a shorter scale length if available, to bring the tension back into the optimal zone.
How to Use This Evertune Tension Calculator
Using this evertune tension calculator is straightforward and designed for quick, accurate results:
- Enter Scale Length: Input the vibrating scale length of your guitar. This is typically measured from the nut to the bridge saddle. Use the dropdown to select between inches (in) or millimeters (mm).
- Enter String Gauge: Input the diameter of the string you are interested in. String gauges are commonly given in "mils" (e.g., 10 for a .010" string) or millimeters. Select the appropriate unit.
- Select Target Note/Tuning: Choose the specific musical note you intend to tune that string to. The calculator provides common guitar notes and their corresponding frequencies.
- Select String Material: Choose the material of your string (e.g., Plain Steel, Nickel Wound). This affects the string's density and thus its unit weight.
- Choose Result Tension Unit: Select whether you want the final tension displayed in pounds (lbs), kilograms (kg), or Newtons (N).
- Click "Calculate Tension": The calculator will instantly display the primary tension result, intermediate values like frequency and unit weight, and a helpful indicator for the Evertune zone.
- Interpret Results & Use Chart: Review the calculated tension and its Evertune zone status. The interactive chart below also visually represents how tension changes with string gauge, helping you understand the impact of different string choices.
- Reset: If you want to start a new calculation, click the "Reset" button to restore default values.
Remember that the "Optimal Evertune Zone" is a general guideline (typically 10-18 lbs per string). Your personal preference and specific Evertune bridge setup might vary slightly, but this range is a great starting point for maximum stability.
Key Factors That Affect Evertune String Tension
Understanding the variables that influence string tension is crucial for optimizing your evertune tension calculator results and achieving the perfect feel on your Evertune-equipped guitar:
- String Gauge (Diameter): This is arguably the most intuitive factor. A thicker string (higher gauge) will require more tension to reach a given pitch than a thinner string, assuming all other factors are constant. Evertune users often experiment with gauges to fine-tune tension within the optimal zone.
- Scale Length: The distance between the nut and the bridge saddle. A longer scale length allows for lower tension for a given pitch and string gauge, or conversely, permits heavier gauges for standard tunings without excessive tension. Baritone guitars utilize longer scale lengths to achieve lower tunings with manageable tension. See our guide on Understanding Guitar Scale Lengths.
- Target Note/Frequency: The desired pitch of the string directly impacts tension. A higher note (higher frequency) demands significantly more tension than a lower note for the same string and scale length. This is why guitar string sets have progressively thinner strings for higher pitches.
- String Material Density: Different string materials have varying densities. For example, plain steel is denser than nylon, and certain wound string materials (like phosphor bronze used in acoustics) have different effective densities than nickel-plated steel. Denser materials contribute to higher unit weight and thus higher tension for a given gauge and pitch. Explore our Guitar String Material Guide.
- Core vs. Winding: For wound strings, the construction (e.g., round core vs. hex core, winding material) can subtly affect the effective unit weight and flexibility, though the calculator uses a generalized density for simplicity.
- Gravitational Constant (gc): While not a variable you change, this constant ensures the units in the formula are consistent, allowing for accurate conversion between mass, length, frequency, and force (tension).
By manipulating these factors, particularly string gauge and scale length, guitarists can dial in the precise tension needed for their preferred playing style, tuning, and to keep their Evertune bridge functioning flawlessly. For specific string gauge recommendations, check out our Guitar String Gauge Chart.
Frequently Asked Questions (FAQ) about Evertune Tension
Q1: What is the optimal tension range for an Evertune bridge?
A: While specific models can vary, the generally accepted optimal operating range for Evertune bridges is typically between 10 to 18 pounds (lbs) of tension per string. Staying within this range ensures the bridge's springs and mechanism can effectively maintain pitch stability.
Q2: Why is string tension so important for Evertune?
A: The Evertune bridge works by balancing the string's tension against a spring mechanism. If the string tension is too low, the spring might bottom out, losing its "zone" and stability. If it's too high, the spring might be overtightened, also causing it to lose its zone and potentially putting excessive stress on the bridge components. The correct tension ensures the system operates in its intended "sweet spot."
Q3: Can I use any string gauge with an Evertune bridge?
A: While Evertune is versatile, you need to select string gauges that, in combination with your scale length and tuning, result in tension within the optimal 10-18 lbs range. Very light gauges in low tunings or very heavy gauges in high tunings might fall outside this range. Our evertune tension calculator helps you determine this.
Q4: How does scale length affect Evertune tension?
A: Longer scale lengths require less tension to achieve the same pitch with the same string gauge compared to shorter scale lengths. This is why baritone guitars (longer scale) can handle very low tunings with manageable string tension, which is beneficial for Evertune systems in those applications.
Q5: My calculated tension is outside the optimal Evertune range. What should I do?
A: If tension is too low, try a heavier gauge string or a higher tuning. If tension is too high, try a lighter gauge string or a lower tuning. Adjusting your scale length (if you have multiple guitars) or consulting a luthier for bridge setup adjustments might also be options. The goal is to bring the tension into the 10-18 lbs zone.
Q6: Why are there different units for string gauge (mils vs. mm) and tension (lbs, kg, N)?
A: Different regions and manufacturers use different measurement systems. "Mils" (thousandths of an inch) is common in the US, while millimeters (mm) are standard in metric systems. Similarly, force (tension) can be expressed in pounds-force (lbs), kilograms-force (kg, though technically mass, it's often used colloquially for force), or Newtons (N), the SI unit for force. This calculator provides options for user convenience and clarity.
Q7: Does string material significantly impact tension?
A: Yes, string material density directly affects its unit weight, which is a key factor in the tension calculation. For instance, a plain steel string of a given gauge will have different tension than a nylon string of the same gauge at the same pitch and scale length due to density differences. Our calculator includes common material options.
Q8: How often should I re-evaluate my Evertune tension?
A: You should re-evaluate tension whenever you change string gauges, significantly alter your tuning, or change your guitar's scale length (e.g., if you get a new instrument). For consistent setups, it's a good practice to check with this calculator periodically or if you feel your Evertune isn't performing as expected.
Related Tools and Internal Resources
Enhance your understanding and setup with these related resources: