Guitar String Tension Calculator - Tension from Pitch, Scale, and Unit Weight

The guitar string tension calculator returns the tension a single string carries when tuned to a chosen pitch on a chosen scale length, given the string's published unit weight. You enter the pitch, scale length, and unit weight, and the calculator returns tension in newtons, pound-force, and kilogram-force, plus the played frequency and wavelength.

• • Comparing string sets: Pick two string gauges, feed each unit weight into the calculator, and see whether the higher gauge raises tension proportionally or whether a step up in pitch on a longer scale creates a heavier pull.
• • Setting up an alternate tuning: Drop your low E to D or C and check the new tension before you restring; tension drops with pitch squared, so a half-step drop cuts tension by about 11%.
• • Matching tension across instruments: If a baritone feels too stiff on .013s, dial in the tension for a comparable string on a 27 in scale and a 25.5 in scale to see whether the baritone actually pulls harder or whether your hand just remembers the shorter scale.
• • Planning a bass or ukulele string change: Use the same calculator for a 34 in bass or a 13.5 in ukulele; the formula T = 4 μ L² f² holds for every stretched string, so one tool covers the family.

The calculator stores everything internally in SI units (meters, kilograms, hertz), so the wavelength output stays in the unit you entered and reads naturally next to the scale length.

Strings and frets share the same scale-length input on a guitar, so a Fret Calculator sits naturally next to a tension check on a new set.

The calculator does two things in sequence: it converts the note-and-octave input into a frequency in hertz using equal temperament, then plugs that frequency into the string vibration equation to return tension.

• μ (unit weight): Linear mass density in kilograms per meter, taken from the string manufacturer's published tension chart.
• L (scale length): Vibrating length from nut to bridge, converted from inches, centimeters, millimeters, or meters to meters.
• f (frequency): Fundamental frequency of the open string in hertz, derived from the note name, octave, and tuning reference using f = A4 · 2^((octave - 4) + semitonesFromA / 12).

Equal temperament divides each octave into 12 equal semitones, so every semitone raises pitch by the 12th root of 2 (~1.059463). Type any note name plus an octave and the right frequency appears.

According to Stanford CCRMA - Pitch and Pitch Perception (String Tension), the fundamental frequency of a stretched string is f = (1/2L) sqrt(T/μ), so solving for tension gives T = 4 μ L² f².

According to Wikipedia - String (music), the tension required to bring a string to a given pitch is T = 4 μ L² f² where μ is the linear mass density, L is the vibrating length, and f is the fundamental frequency.

The semitone step from one pitch to the next is a factor of 2^(1/12), and a Log 2 Calculator makes that same binary logarithm visible for any positive input.

Four building blocks determine how much pull a guitar string puts on the neck, and each shows up as an input or output here.

Pitch drives tension quadratically, while scale length and unit weight appear linearly in T. Dropping a low E to D cuts tension by about 22% on a typical guitar string tension chart.

Once the calculator has produced a frequency in hertz, a Frequency Calculator takes any wavelength or period input and returns its frequency the same way the tension formula uses the pitch.

Type the open-string pitch, scale length, and unit weight, and read the tension straight off the result panel.

1. 1 Pick the note name and octave: Select the open-string pitch class and the scientific-pitch-notation octave. For standard six-string tuning the low E is E2 and the high E is E4; for a five-string bass low B is B0.
2. 2 Confirm the tuning reference: Leave A4 at 440 Hz unless you are deliberately modeling 432 Hz, 442 Hz, or another standard. Changing A4 by 1 Hz scales every frequency by the same factor and pushes tension by the squared percentage.
3. 3 Enter the scale length and pick a unit: Use the manufacturer's spec sheet (25.4 in for a Martin acoustic, 25.5 in for a Strat, 34 in for a standard bass). Switch units if your spec sheet lists the scale in millimeters; the formula reads meters regardless.
4. 4 Type the string unit weight: Look up the unit weight from the string manufacturer's tension chart (D'Addario, GHS, and Elixir all publish one). Plain-steel strings usually run 0.3 to 1 g/m; bass wound strings reach 90 g/m.
5. 5 Read tension in three units: Pound-force sits up top because manufacturer charts are in pounds, with newtons and kilogram-force underneath. Frequency and wavelength (2 × L) live in the same panel for sanity-checking the pitch input.

To check whether your .010 set will hold tune on a 25.5 in Strat: leave A4 at 440, set scale length to 25.5 in, set note E and octave 4, type the manufacturer unit weight (around 0.40 g/m for a typical .010 plain steel), and read the tension. A result near 16 lbf means the high E matches the EXL110 published tension and the rest of the set will fall in line.

When an alternate tuning makes a chord shape uncomfortable, the Chord Transposer moves the same progression into a new key while this calculator confirms the new tuning keeps tension under control.

Five practical gains when you move from a paper string tension chart to a live calculator.

• • Catch tension before you restring: Type the new string's unit weight and the new tuning and read tension in seconds, instead of trusting your memory of the chart on the package.
• • Compare guitars on the same page: Toggle the scale length between 24.75 (Les Paul), 25.5 (Stratocaster), 27 (baritone), and 34 (bass) and watch the same string choice behave differently.
• • Read tension in three units at once: Pound-force sits up top for manufacturer charts, with newtons and kilogram-force underneath for physics and metric spec sheets.
• • Test alternate tunings without re-tuning: Drop the low E to D by switching the octave, see the tension drop by about 22%, and decide whether the neck needs a setup adjustment before you actually detune.
• • Cover bass, guitar, and ukulele with one tool: The formula T = 4 μ L² f² is identical for every stretched string, so the same inputs work for a .046 nickel-wound bass low E and a nylon ukulele G.

The biggest payoff is the scale-length comparison: switching from 25.5 in to 24.75 in on the same gauge drops guitar string tension by about 6%, the exact feel difference between a Stratocaster and a Les Paul.

Because frequency doubles every octave, a Geometric Sequence Calculator plots the same geometric series for any first term and ratio and makes the doubling clear without leaving the page.

Three physical inputs and three approximations bound how far you can push the formula before a real string behaves differently.

• • The calculator models a uniform, perfectly flexible string under ideal tension. Real strings add bending stiffness from the core wire, so high frets and very thin strings at high pitch can deviate by a few percent.
• • Manufacturer-published tensions assume the string is fresh, at room temperature, and tuned to a specific A reference. Old, cold, or stretched strings carry different tension at the same dial reading.
• • Bass strings with very heavy gauges have non-uniform mass distribution because the wrap does not sit perfectly concentric with the core; the unit weight still captures the average, but the pluck response can vary.

Treat the output as the nominal tension the string carries on the nut-to-bridge span, then apply compensation for temperature, age, and playing style.

According to D'Addario String Tension Pro Calculator, the company's published tension values use the same T = 4 μ L² f² relation with each string's published unit weight.

When the result drifts from a published chart, a Wave Speed Calculator confirms the same T and μ yield the expected wave speed, since v = sqrt(T/μ) is the same physics.