Step 1
Base tension by string type
Poly: 48.5 lbs
Co-Poly: 49 lbs
Synthetic Gut: 55 lbs
Multifilament: 54 lbs
Natural Gut: 55.5 lbs
Hybrid: 52.5 lbs
Reference Guide
How the Tension Calculator Works
This page explains the current starting-tension formula used in Tennis String Lab. It is designed to be transparent: base tension by string type, plus simple adjustments for string gauge, racket family, court surface, feel goal, arm comfort, and the displayed result window.
Formula Overview
What the calculator adds together
Step 2
Racket family adjustment
Pure Drive / Clash / Power Frame: +1.5 lbs
Ezone: +1 lb
Blade / Pro Staff / Head Speed / Head Radical / Control Frame: +0.5 lbs
Pure Aero / VCORE / Spin Frame: +0 lbs
Step 3
String gauge adjustment
15L: +1 lb
16: +0.5 lbs
16L: 0 lbs
17: -0.5 lbs
17L: -0.75 lbs
18: -1 lb
Step 4
Feel goal adjustment
Comfort: -2 lbs
Balanced: 0 lbs
Control: +2 lbs
Step 5
Court surface adjustment
Hard Court: 0 lbs
Clay: +1 lb
Grass: -1 lb
Indoor: +0.5 lbs
Step 6
Arm comfort adjustment
Normal: 0 lbs
Sensitive: -1.5 lbs
Very Sensitive: -3 lbs
Step 7
Clamp and displayed range
The target number is capped between 42 and 58 lbs. After that, the tool shows a practical window of target +/- 1.5 lbs and converts that range to kilograms.
Step 8
Nearby string references
The result also pulls in nearby references from the database. It looks for entries with the same string type and the closest stored tension band so the user sees realistic comparison points, not just raw formula output.
Worked Example
How one recommendation is built
Inputs
Example setup
String Type: Co-Poly
String Gauge: 17
Racket Family: Control Frame
Court Surface: Clay
Feel Goal: Balanced
Arm Comfort: Normal
Math
Formula result
49 base + -0.5 gauge + 0.5 racket + 1 surface + 0 feel + 0 arm = 50 lbs target
Display
What the user sees
That 50 lbs target displays as roughly 49-52 lbs, plus the kilogram equivalent, because the tool shows a small practical range rather than pretending to know one perfect number.
Important Context
What this number is and is not
Starting Point
Useful, not absolute
The calculator gives a practical starting zone, not an exact personalized answer. It is there to help a player get into the right ballpark before they fine-tune on court.
What still matters
Real setup variables go beyond this formula
Gauge, weather, string age, string pattern, ball type, altitude, machine calibration, and player feel can all move the right answer a little higher or lower than the starting estimate.
Best Use
Test in small steps
Once you have a starting range, change tension in small steps like 1-2 lbs. That makes it easier to learn what you actually respond to without losing the character of the setup.
With Quick Setup
Better when used together
If you apply a recommendation from the Quick String Setup Tool, the Tension Calculator can pre-populate the matching string type and racket family. That gives the calculator a more relevant starting context right away.