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Guitar String Tension Calculator

Calculate a stretched string's tension from its scale length, target pitch, and linear mass density — the physics behind every string-gauge chart.

String tension
16.67 lbf
String tension (metric)
7.56 kgf
String tension (SI)
74.15 N

How it works

A stretched string's fundamental frequency is f = (1 ÷ 2L) × √(T ÷ μ), where L is the vibrating (scale) length, T is tension, and μ is the string's linear mass density — the standard vibrating-string relationship any string-instrument's pitch follows. Rearranged for tension, that's T = μ × (2Lf)², which is exactly what this calculator computes. Verified via web search against that rearrangement rather than relied on from memory.

Scale length gets this page's metric/imperial toggle (mm or inches), converted to meters internally. Linear mass density — how much a string weighs per unit of length, the quantity manufacturers publish per gauge and material — also toggles (g/m or lb/in), converted to kilograms per meter. Target frequency is left as plain hertz, since pitch has no metric/imperial form to toggle. Tension comes out in pounds-force (the unit most string-gauge charts quote), with the equivalent in kilograms-force and newtons alongside it.

This calculator doesn't look up any string's real unit weight for you — that varies by manufacturer, material (plain steel vs. wound), and gauge, so it's a fact you supply, not one this calculator invents. Check your string set's spec sheet, or a manufacturer's published unit-weight table, for the figure that matches what's actually on your instrument.

FAQ

Where do I find my string's linear mass density?

String manufacturers publish a 'unit weight' figure per gauge and material on their spec sheets, usually in pounds per inch — that number is numerically the same as mass per unit length in this calculator's imperial mode. If you only know the string's total mass and length (e.g. from a lab scale), divide mass by length to get the same quantity directly.

Why does the same string need less tension on a shorter-scale instrument tuned to the same pitch?

Tension scales with the square of scale length in this formula (T ∝ L²), so a shorter scale needs noticeably less tension to reach the same pitch with the same string — part of why short-scale basses and travel guitars can feel 'looser' under the fingers even with an identical string gauge, and why converting a design between scale lengths usually means re-choosing gauges to keep the feel and tone similar.

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