String Tension Calculator
How hard is each string pulling? Pick your tuning, set and scale length to see per-string tension, how it compares to standard, and which gauges would bring the feel back.
How to Use the Calculator
- Choose your tuning. Standard is the reference; everything is reported relative to it.
- Pick the set you normally play, or type gauges directly into the table. Gauges are in thousandths of an inch, so a .046 low E is entered as 46.
- Set your scale length. It is printed in your guitar's specifications; if you are unsure, 25.5″ for Fender-style and most acoustics, 24.75″ for Gibson-style.
- Read the table. Each string shows its tension, how far it is from that string in standard tuning, and a plain-language feel. The panel underneath suggests single-string gauges that would bring the feel back.
The Formula
String tension has a closed-form answer, and every string maker uses the same one:
T = UW × (2 × L × F)² ÷ 386.4
T is tension in pounds. UWis the string's unit weight in pounds per inch — how much a one-inch length of it weighs. L is the vibrating length in inches, the scale length. F is the frequency in Hz, which we take from the same note table our tuner listens for. 386.4 is the acceleration of gravity in inches per second squared, there to turn mass into weight.
The two squared terms are what matter in practice. Double the scale length or the pitch and the tension quadruples. Go up one semitone and the pitch rises 5.95%, so the tension rises about 12%; go down one and it falls about 11%. Six semitones — Drop B on the low string against standard E — leaves 50%.
Where the unit weight comes from
A plain steel string is a cylinder of steel, so its unit weight is exactly its cross-sectional area times the density of steel (0.2833 lb/in³). No guesswork.
A wound string is a steel core wrapped in nickel-plated steel, and the proportion of core to wrap changes with gauge, so there is no exact formula. Instead we fit a curve to the unit weights string makers publish for their nickel-wound sets. It lands within about 3% across the .020 to .060 range, which is a smaller gap than exists between two brands of nominally identical strings. Bronze-wound acoustic strings fall within a similar margin.
Why Tension Is Worth Knowing
Tuning down
This is the most common reason to look. A 10–46 set in Drop C loses a third of its tension on the low string, and the result is a string that buzzes, goes sharp when you fret it hard, and will not hold pitch through a bend. The fix is not a higher action; it is a heavier string. The calculator tells you which one — and, just as usefully, which strings don't need changing. In Drop D only the sixth string moves, so only the sixth string needs a heavier gauge.
Balanced tension
Standard sets are not balanced. Look at 10–46 in standard tuning: the plain B string carries about 15 lb while the wound D carries over 18. Some players prefer sets where every string pulls about the same, because bends feel consistent across the neck. Type gauges into the table and watch the column until the numbers line up.
Changing scale length
Moving from a 25.5″ to a 24.75″ guitar with the same set drops tension by about 6% everywhere — the reason a Les Paul with 10s feels close to a Strat with 9.5s. Baritones go the other way: at 27″ a heavy set tuned to B feels roughly like a regular set at standard, which is the whole point of a baritone.
Neck relief and setup
The neck is a spring under the strings' combined pull. Change the total by more than 10% or so and the relief changes with it — less tension lets the neck straighten and you get buzz; more bows it forward and the action rises. If the total in the calculator moves significantly, expect to adjust the truss rod, and probably the intonation too, since a heavier string needs a slightly longer effective length.
Reading the Suggestions
The panel below the table finds, for each string, the stocked gauge whose tension in your chosen tuning is closest to what that string carries in your chosen set at standard pitch. It only searches gauges you can actually buy as singles, so the answer is something you can act on rather than a theoretical .0473.
Strings that change are highlighted. Load the suggestions and the table updates, still measured against your original set, so you can see exactly how close the new gauges land. Then find the packaged set nearest to them, or buy singles — most shops stock every gauge on the list.
After restringing, tune with the chromatic tuner and give a new heavy set a day to settle; wound strings stretch noticeably in their first hours.
Frequently Asked Questions
What is a normal amount of string tension?
A regular light electric set (10–46) on a 25.5-inch scale in standard tuning carries around 104 lb (47 kg) in total, or 15–20 lb per string. Light acoustic sets (12–53) sit near 160 lb. There is no right number — it is what you are used to that matters, which is why the calculator reports every result as a percentage of your own set in standard tuning.
How much does tuning down reduce tension?
Each semitone lowers tension by about 11%, because tension scales with the square of frequency and a semitone is a 5.95% change in pitch. A half step down is roughly 89% of standard; a whole step is about 79%; Drop C's low string, two whole steps down, carries only about 63% of its standard tension.
Which gauge should I use for Drop C or Drop B?
The set that gives each string close to the tension you are used to. Set the tuning and your normal set in the calculator and read the suggested gauges — for Drop C on a 25.5-inch scale, a player used to 10–46 will typically land on something like 11–56 or 12–60. Then buy the closest packaged set, or singles.
Why does the scale length matter?
Tension goes with the square of the vibrating length. The same string tuned to the same note is about 6% tighter on a 25.5-inch Fender scale than on a 24.75-inch Gibson scale. It is why Les Pauls feel slinkier than Stratocasters with identical strings, and why baritones can run heavy gauges at low pitches without going floppy.
How accurate are these numbers?
Within about 1% for plain steel strings, which are pure geometry, and within roughly 3% for wound strings, where the ratio of core to wrap varies between makers. That is smaller than the difference between two brands of the same gauge. The percentages and the gauge suggestions, which are what you act on, are more robust than the absolute figures.
Should the 3rd string be plain or wound?
Electric sets use a plain 3rd up to about .020; acoustic sets and heavier electric sets use a wound 3rd from around .020 to .026. The calculator guesses wound at .020 and above, and the type button on each row lets you override it — a plain and a wound string of the same gauge differ in tension by about 10%.