Methodology

A TTDNA rating runs from 0 to 100 and means the same thing everywhere on this site. 80 on a Butterfly sheet is 80 on a DHS sheet, and the same scale is used when blades are rated. There is no second set of numbers to reconcile, no per-brand conversion table, no asterisk on half the catalogue.

The reason is simple: a rating is only useful if it can be compared. Manufacturers each invent their own range, their own zero point and their own idea of what a 10 in control is. Line up four brands on one page and the numbers cancel each other out. One scale, made in one place, under one set of rules, is the only version of this that survives contact with a real comparison.

Brand specifications are written to sell the product. They are set by the people who launched it, usually against the brand’s own back catalogue, and they move when a new flagship needs room above the old one. That is marketing material, and it is perfectly normal — it just is not measurement.

TTDNA ratings are built the other way around: fixed inputs, fixed rules, no brand loyalty, no launch to protect. A sheet does not score higher because it is new or because its maker wants it to. Where a brand’s own figures interest you, read them at the source — the manufacturer’s product page is the only place they are authoritative, and this site will not reprint them as if they were ratings.

Every rating traces back to six core numbers:

Speed · Spin · Control · Arc · Hardness · Tackiness

Those are set from the physical properties of the sheet — sponge hardness, topsheet grip, surface type, measured and published construction data — and from the behaviour that surface family reliably shows in play. Everything else on a product page is calculated from them. The same input produces the same output on every page load. Nothing is randomised, nothing is hand-tuned per product, and no rating exists that cannot be reproduced from the six numbers above.

These are the exact derivations. Hardness is sponge hardness on the normalised degree reference.

Power             = 0.70 x Speed   + 0.30 x Hardness
Grip              = 0.75 x Spin    + 0.25 x Tackiness
Catapult          = 0.55 x Speed   + 0.25 x (100 - Hardness)
Throw angle       = 0.60 x Arc     + 0.25 x Spin      + 0.15 x (100 - Hardness)
Elastic           = 0.50 x Speed   + 0.50 x Catapult
Spin sensitivity  = 0.60 x Grip    + 0.40 x Spin      - 4 if Tackiness <= 50
Short game        = 0.70 x Control + 0.30 x (100 - Speed)
Blocking          = 0.60 x Control + 0.20 x (100 - Hardness) + 12
Backhand flip     = 0.50 x Spin    + 0.30 x Control   + 10
Counterloop       = 0.50 x Speed   + 0.35 x Spin      + 0.15 x Control
Opening loop      = 0.55 x Spin    + 0.25 x Arc       + 0.20 x Control
Chop              = 0.60 x Control + 0.40 x (100 - Speed)
Serve             = 0.60 x Spin    + 0.25 x Control   + 0.15 x Tackiness
Service receive   = 0.55 x Control + 0.45 x Short game
Difficulty        = 0.45 x Speed   + 0.30 x Hardness  + 0.25 x (100 - Control)
Beginner friendly = 100 - 0.85 x Difficulty
Durability        = 70 + 0.06 x (100 - Tackiness) - 0.15 x (Speed - 70)

Six inputs feed everything: Speed, Spin, Control, Arc, Hardness, Tackiness.
Arc is the shape of the ball path. Throw angle is how high the ball leaves the
rubber. They are separate inputs and are never treated as the same number.
Catapult and Short game are chained into Elastic and Service receive before
rounding, so no drift builds up. Every result is rounded and clamped to 0-100.

When a core number cannot be established for a specific model, the surface family supplies it. These are the only baseline values in the system, and they are the reason an obscure long-pips sheet still gets a full rating set instead of a page of blanks.

Thickness options and OX are variants of one model, not separate products. A variant starts from the base sheet and is shifted by fixed rules, so a variant comparison shows the shifted rating rather than the base sheet.

Inverted     1.5 mm and under   Speed -5   Spin -2   Control +4   Power -6   Short game +4
Inverted     1.6-1.8 mm         Speed -3   Spin -1   Control +2   Power -4   Short game +2
Inverted     1.9-2.0 mm         reference sheet, no shift
Inverted     2.1-2.2 mm         Speed +2   Spin +1   Control -1   Power +3
Inverted     Max                Speed +3   Spin +2   Control -2   Power +4
Long pips    OX                 Speed -6   Power -7  Blocking +4  Short game +4
Anti-spin    OX                 Speed -5   Power -6  Blocking +4  Short game +3

Short pips and medium pips follow the same thickness pattern as inverted, with the shift applied to blocking instead of spin. OX exists only where it exists in reality: long pips and anti-spin. A thickness rule never moves a rating by more than 8 points.

Two products are compared on the full rating set, every time. Nothing is dropped because one side is thinner on data.

• Differences below the tie tolerance are reported as similar, not as a win for either side.
• Some ratings are neutral — tackiness, arc, catapult, throw angle, elasticity, spin sensitivity, difficulty. Higher is not better there, only different.
• Player-profile similarity weights the ratings differently per playing style. What comes out is a match for that style, not an overall quality score.

If a rating looks wrong, report it with the model name and what you are basing it on. The fix goes into the inputs so it propagates everywhere, rather than being patched on one page.