String gauge in thousandths and how tension changes with tuning
I put a set of 'nines' on my guitar and it felt like I was playing rubber bands. Went back to tens the next day. The difference between 0.010 inches and 0.009 inches on the high E is a thousandth of an inch — smaller than a human hair — and it changes the entire feel of the instrument.
Guitar strings are gauged in thousandths of an inch. A '10s' set has strings at 10, 13, 17, 26, 36, 46 thousandths (0.010, 0.013, 0.017, 0.026, 0.036, 0.046 inches). '9s' are 9, 11, 16, 24, 32, 42. The unwound treble strings (top three) are plain steel; the bass strings are wound. Manufacturers vary by 1-2 thousandths per string across brands even at the same nominal set name.
Tension is what you feel
String tension at standard tuning (E-A-D-G-B-E) for a 10s set on a 25.5-inch scale (Strat): high E ~16 lb, low E ~19 lb, total across the six strings ~110 lb. On a 24.75-inch scale (Les Paul), same strings pull ~100 lb because scale length matters. Tension in pounds is what your fingers experience as 'stiff' or 'slinky'.
What drop tuning does
Drop the whole guitar a whole step (D standard) and tension falls to about 78% of standard = 86 lb total for 10s. The strings flop. Compensation: use heavier gauge for lower tunings — 11s for D standard, 12s or 13s for C. Rock and metal players who tune low buy heavier strings for this exact reason.
Scale length interaction
A baritone guitar (27-30 inch scale) uses medium gauge strings tuned low because the longer scale keeps tension in the same feel-range as a regular guitar with lighter strings at standard tuning. Bass guitars work the same way — longer scale, thicker strings, tuned low.
Recap
Gauge in thousandths determines tension. Tuning and scale length modify tension by the square of frequency. Pick gauge to match tuning, not always to 'standard'.
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FAQ
What about acoustic strings?+
Similar gauges but wound differently and typically heavier (12s or 13s standard) because acoustic bodies need string energy to project.
Does string material matter?+
Yes — nickel vs stainless vs pure nickel change tone; coated strings last longer; but for tension, mass per length is what matters and gauge captures it.
This article was written by The Turbo Unit Converter engineering desk (Applied metrology & engineering units) and last reviewed on 2026-07-23 against NIST SP 811 and the BIPM SI Brochure. Read our full editorial policy.