Scale length & tuning
String tension comparison
Use this free string tension calculator to compare the same string at two scale lengths or tunings. See the percentage change before planning a different setup. No email or account needed.
Compare string tension
Keep the string’s gauge, material and construction the same. Enter the old and new scale lengths, then the change in pitch.
Start with the change you want to compare
Comparing two guitars? Enter each instrument’s stated scale length and leave pitch change at zero if both use the same tuning. Comparing tunings on one guitar? Keep both scale lengths identical and enter the pitch difference. To explore both changes together, update all three fields.
The original setup is your reference point. A result of 94.2% means the new tension is 94.2% of that reference, or 5.8% lower. It does not mean the string has lost 94.2% of its tension. Reset returns to the 25.5-inch versus 24.75-inch example.
Use inches or millimetres for both lengths; the unit selector converts the numbers already entered. Check the actual specification for your instrument instead of relying on the brand name. For a multiscale instrument, use the length of the particular string you are comparing.
Three examples to try
- 25.5 to 24.75 inches, same tuning: enter 25.5, 24.75 and 0. The result is about 5.8% less tension. Reversing the comparison gives about 6.2% more, because the starting reference changes.
- Half a step down, same guitar: enter the same length twice and −1 semitone. The result is about 10.9% less tension on each unchanged string tuned down by that amount.
- One string down a whole step: keep the scale lengths equal and enter −2. The result is about 20.6% less tension on that string. It is not a 20.6% reduction in the total pull of a set when only one string changes.
These are mathematical comparisons, not recommendations to retune an instrument. To compare a different gauge or a different string brand, use the exact string specifications instead. Our string gauge recommendation tool can help you explore a starting set for your playing style.
How the comparison is calculated
D’Addario’s string tension explanation gives tension as a function of string unit weight, vibrating length and pitch. For the same string, unit weight cancels when dividing the new tension by the old tension. Using equal-tempered semitones gives:
New tension ÷ original tension = (new scale ÷ original scale)2 × 2(semitone change ÷ 6)
The tool multiplies that ratio by 100 to show a percentage of the original, and subtracts 100 to show the percentage change. It rounds displayed percentages to one decimal place. It cannot calculate absolute force without the string’s unit weight; for that, consult the manufacturer’s String Tension Pro calculator and exact string data.
Turn the comparison into a setup check
Write down your current strings, tuning and measurements before experimenting. After settling on the strings and tuning you actually want to play, check the instrument again. A percentage result does not tell you how far to turn a truss rod or move a saddle.
Use the guitar setup calculator for model-specific starting specifications, then work through the intonation checker if fretted notes need attention. If you are working on a Fender and want a printable measurement sequence and setup record, see the Fender Setup Guide PDF.
String tension questions
Can I compare a 25.5-inch and a 24.75-inch scale?
Yes. Enter 25.5 as the original scale, 24.75 as the new scale and 0 for pitch change. For the same string at the same pitch, the shorter scale gives about 5.8% less tension. Reverse the lengths to compare in the other direction.
How do I enter E standard to E-flat or drop D?
For E standard to E-flat, use −1 semitone for every string. For drop D, the low E string moves down two semitones, so enter −2 for that string only. The other five strings stay at 0. This tool compares one string at a time.
Can this tell me which heavier gauge replaces my current strings?
No. It assumes the same string and the same unit weight throughout. Changing gauge, core, winding or material breaks that assumption. Use a manufacturer’s data for the exact strings when comparing replacement sets.
Does the percentage tell me how easy a bend will feel?
No. It describes the change in static tension under the stated assumptions. Action, string construction, bridge behaviour and playing technique also affect what you experience. Treat the result as one comparison, then assess the guitar at its final tuning.
Does this calculator check whether a tuning is safe?
No. It does not know your instrument’s condition, bridge, neck, string specification or intended tuning range. The allowed input range is only a calculator boundary. Follow the instrument and string manufacturers’ guidance for your equipment.