How your rating is calculated
Every player has an ELO rating — a single number that captures how strong you are. It goes up when you win and down when you lose, but how much depends on who you played. Here's the whole system, no black box.
- Starting rating
- 1000
- Max swing per match
- ±32
Step 1
What was expected
Before a match, the system works out how likely each player was to win, from the gap in ratings. A bigger gap means the favourite is expected to win more often. This expected score is a number between 0 and 1 — think of it as your win probability.
E = 1 / (1 + 10(opponent − you) / 400)
A 400-point lead means you're expected to win about 9 times out of 10. Equal ratings mean a coin flip — an expected score of 0.5 each.
Step 2
Adjust for what happened
After the match, your rating moves by the K-factor times the difference between what actually happened (1 for a win, 0 for a loss) and what was expected:
new = old + 32 × (result − expected)
Beat someone you were expected to beat and you gain only a little. Beat someone far above you and you gain a lot — and they lose the same amount. It's a zero-sum exchange.
A worked example
Say you're rated 1000 and you beat an opponent rated 1200 — a clear underdog win.
- 1
Expected score: E = 1 / (1 + 10200/400) ≈ 0.24. You were expected to lose.
- 2
You won, so result = 1. Change = 32 × (1 − 0.24).
You climb to 1024; your opponent drops the same 24 to 1176.
Had the favourite (1200) beaten you instead, they'd have gained only about +8 — the result everyone expected, so barely any movement.
Singles, doubles & teams
Singles and doubles are separate ladders. You carry an independent rating in each, both starting at 1000, so a doubles specialist and a singles specialist are never mixed up.
In doubles, a team's strength is the average of its two players' ratings, and that team average is what the formula compares. When a team wins, both partners gain the same number of points; when it loses, both lose the same. Your own rating still moves from your own starting point — beating a strong pair lifts a lower-rated partner more in absolute terms.