Tension calculator
What tension shouldthe new string go on at?
You already know what your current setup feels like. Tell us what you play now and what you are switching to, and this scales the lab-measured bed stiffness between them to give you a starting tension — so the new string arrives feeling like the old one rather than like a stranger.
Why this is a scaling and not a lookup
Most of this database was tested at three reference tensions — 40, 51 and 62 lb — so for those strings there is a real stiffness-versus-tension curve to solve rather than a rule to apply. The calculator fits a line through the measured points for each string and finds the tension at which the new one reproduces the bed you have now.
A string bed carries stiffness that does not come from tension at all: fitting the measured points gives an intercept around 60-65 lb/in before any tension is applied. That is why proportional scaling overshoots, and why the measured model is the better answer where the data exists. Luxilon ALU Power measures 183 lb/in at 40 lb and 248 at 62 — scaling its 51 lb figure proportionally would have predicted 164 at the bottom end and been wrong by nearly 20 lb/in.
Where a string has not been tested at every tension, the calculator says so and falls back to proportional scaling — which is what stringers already do by feel. Either way the page tells you which of the two answers you are looking at.
It cannot tell you what tension to start at if you have never strung a racquet before — it converts between two strings, it does not invent a baseline. If you have no current setup to convert from, string in the middle of the range printed on your frame and adjust from there.