Calculate tennis racket swingweight after adding lead tape or weight at a set distance from the butt, or the mass needed to reach a target swingweight.
Tennis Racket Swingweight Formula or Method
A point mass changes swingweight according to its mass and squared distance from the standard 10 cm butt pivot.
How the Calculation Works
Choose updated swingweight or added mass required. The inverse rearrangement is added mass (g) = (target − base swingweight) × 1000 ÷ (placement in cm − 10)². Only source fields are shown; values are retained when switching modes and hidden fields do not block validation. This calculator does not solve for placement.
How to Use This Calculator
- Select the result you want in the Solve for menu.
- Enter the base swingweight, added mass or target, and placement; racket length defaults to 27 in (68.58 cm). Select centimeters or inches for each length; changing units converts the same quantity.
- Select Calculate and review the answer and substituted steps.
- Use Reset before starting a different sample.
Worked Example
Adding 4 g at 55 cm increases swingweight by 8.10 kg·cm², moving a 320 racket to about 328.10 kg·cm².
Input and Result Guide
| Item | How to use it |
|---|---|
| Base swingweight | Use a measured or published swingweight about the same 10 cm butt axis. Mass, balance, and length alone do not determine it. |
| Added mass | Enter the total mass added at the stated location. |
| Distance | Measure from the butt end to the added mass center. |
Interpreting the Result
Compare base and target values about the same 10 cm butt axis and verify the finished racket on a swingweight machine. Adding nonnegative mass cannot reduce the modeled swingweight. An inverse result above 500 g remains visible with an explicit warning rather than being clamped.
Assumptions and Limitations
The point-mass model is an estimate. Replacing distributed tape with a point at its center omits the tape’s own moment about that center. Zero mass, or an ideal point mass at the 10 cm pivot, gives zero modeled increase. At that pivot an unchanged target does not determine a unique mass, while a positive increase has no finite point-mass solution. The calculator uses the controlling 73.7 cm overall-length bound and checks placement within the racket; it does not verify all equipment rules. Its base, target, and input-mass bounds are operational calculator limits rather than modification recommendations.
Common Questions
Why did an input disappear when I changed Solve for?
The hidden field is the requested output. Enter the remaining visible values and the calculator will solve for that target.
Will my last successful calculation be restored?
Yes. A successful calculation saves a versioned input and unit snapshot in this browser, including the original exact quantities behind converted length displays. Results are recomputed on return without storing result HTML. Editing a length replaces that field’s conversion basis. Other scripts on this site may access saved values. Reset clears this calculator’s saved data.
Sources
Tennis Warehouse University’s racket-weighting analysis describes the 10 cm butt axis and point-mass inertia relationship. Appendix II of the 2026 ITF Rules of Tennis gives the 73.7 cm length limit and states that SI units take precedence; the printed 29-inch equivalent is approximate.
