Who runs this site, how it was made, and how far to trust the numbers.
String Tension Calculator is a free tool that works out the tension of each string on a guitar, bass or ukulele from its gauge, construction, tuning and scale length. It runs entirely in your browser and isn't tied to any string manufacturer.
This is an independent project that operates under the site name. It doesn't present a named expert, because the numbers don't rest on any one person's credentials. They rest on a published physics formula, published material data and tension charts published by string makers, all of which you can check yourself on the Methodology page.
The calculator and the text on this site were built with the help of an AI assistant (Claude, by Anthropic). The calculation is checked by an automated test suite against D'Addario's published tension charts, and the results of those checks, including where accuracy is weaker, are listed on the Methodology page.
Many tension calculators are tied to one brand's strings or don't explain where their numbers come from. This one shows its method, accepts any gauge and doesn't ask for an account.
Results are estimates, not manufacturer specifications. Plain-string and phosphor-bronze predictions land within about 1% of published charts, the 10-46 nickel wound set within 2%, and heavy bass strings can be off by up to 8%. Confirm unusual setups with your string maker. This site has no affiliation with D'Addario or any other brand; their published charts are used only as a reference to test against.
Write to hello@stringtensioncalc.com if a figure disagrees with a manufacturer's chart or you find a mistake. Corrections that change a result are noted on this page with their date.
Last updated: 7 October 2026