The formula
new TTR = old TTR + round[(result − expected result) × K]
- Result: the number of singles you won in the event.
- Expected result: the sum of your win probabilities against each opponent.
- K: the change constant, between 16 and 32 (below).
Win probability
Your chance of beating an opponent depends only on the difference between your two ratings:
P(win) = 1 / (1 + 10(opponent’s TTR − your TTR) / 150)
Equal ratings give 50 %. Every 150 points of difference multiply the odds by ten, so a gap of a few hundred points makes the result almost certain — and a loss to a much weaker player costs nearly the whole change constant.
| TTR difference | Stronger player wins | Weaker player wins |
|---|---|---|
| 0 | 50.0 % | 50.0 % |
| 25 | 59.5 % | 40.5 % |
| 50 | 68.3 % | 31.7 % |
| 100 | 82.3 % | 17.7 % |
| 150 | 90.9 % | 9.1 % |
| 200 | 95.6 % | 4.4 % |
| 300 | 99.0 % | 1.0 % |
| 400 | 99.8 % | 0.2 % |
The change constant
The change constant (Änderungskonstante) sets how fast a rating moves. It starts at 16 and rises by 4 for each of these:
- under 21,
- under 16 (another 4, so 8 in all for players under 16),
- fewer than 30 rated singles so far,
- no rated event in the last 365 days — for the next 15 singles.
That makes it 16 for an established adult player and up to 32 for a young newcomer returning from a break, whose rating is the least certain.
One event, rounded once
The wins and the expected wins are added up over all your singles in the event, and the change is rounded once — not per match. Two wins at 1600 against two players rated 1500, with K 20, give +7; rounding each single on its own would have given +8.
| Your TTR | Singles | K | Expected | Change | New TTR |
|---|---|---|---|---|---|
| 1500 | won vs 1500 | 16 | 0.50 | +8 | 1508 |
| 1600 | won vs 1500, won vs 1500 | 20 | 1.65 | +7 | 1607 |
| 1800 | lost vs 1400 | 16 | 1.00 | −16 | 1784 |
| 1450 | won vs 1520, lost vs 1610 | 16 | 0.33 | +11 | 1461 |
What the formula does not cover
- Sets and points: only whether you won or lost each single counts.
- Youth growth points, which the official list adds every quarter to young players.
- The deduction for long inactivity.
Neither of the last two belongs to an event, so no per-event calculation can show them. New players are placed between 720 and 900; the top of the German list is near 2,400.
Source
Formula, probability and change constant follow the DTTB’s “Beschreibung der andro-Rangliste” (as of 14 August 2025). Every number on this page is computed with the same code as the calculator in the app. It shows what the published formula gives for the singles entered; the official rating is the one on myTischtennis.
Work out your next TTR
Trainoro’s rating calculator does this for every league match and tournament: enter your TTR and your opponents’, mark wins and losses, tick what applies to the change constant, and see your new rating. It runs on your phone, with no login.
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Scan a code with your phone's camera, or tap the link.