Guitar String Tension Calculator
Work out how much tension each string pulls — and the total across the whole set — before you change gauges, tune down, or set up a new guitar. Enter your scale length, tuning, and string gauges below; everything is computed instantly in your browser.
How the numbers are calculated
The calculator uses the standard, public-domain vibrating-string tension formula that string manufacturers publish for their own tension charts:
T = UW × (2 × L × F)² ÷ 386.4
- T — tension in pounds (lb)
- UW — unit weight (weight per inch of string, lb/in)
- L — scale length in inches
- F — the note's frequency in Hz (equal temperament, A4 = 440 Hz)
- 386.4 — gravitational constant in in/s² (converts mass to force)
Unit weight is estimated from the string's diameter and construction using standard approximations, not brand-specific measured data:
- Plain steel: UW = 0.2215 × d², derived directly from the density of music-wire steel (~0.284 lb/in³). This matches published plain-string weights closely.
- Wound strings: UW = C × d², where C ≈ 0.140 (nickel-wound), 0.144 (pure nickel) and 0.150 (phosphor bronze) — average linear-density coefficients for each wrap/core construction.
These are widely-used physics approximations. Real-world tension varies by roughly ±5% depending on brand, core-to-wrap ratio, and winding, so treat the results as a close estimate rather than an exact spec for one specific string. The feel rating compares your total tension to typical ranges (electric ≈ 84–104 lb, acoustic ≈ 120–150 lb for a standard 6-string) and is a rough guide only.
Why string tension matters
Tension is what you feel under your fingers and what your guitar's neck, bridge, and (on a Strat) tremolo springs have to balance against. Moving up a gauge or tuning down a couple of steps can swing total tension by 10–20 lb — enough to change the action, throw off intonation, and, with a floating tremolo, tilt the bridge. Checking tension before you commit saves a second trip through your setup.