Elo Calculator
Enter two ratings and a result to see how many points each player wins or loses. It uses the same Elo formula as every game on Custom Elo Games.
What is Elo?
Elo is a rating system that turns a history of results into one number per player. It was devised by physics professor Arpad Elo and first adopted by the US Chess Federation in 1960, and it is now used everywhere from chess to online games and office ping-pong ladders.
A higher number means a stronger player, and the gap between two ratings predicts how a match between them should go. Every result moves points from the loser to the winner — and how many depends on how surprising the result was. Beat someone rated well above you and you gain a lot; beat someone well below you and you barely move.
How Elo is calculated
First, each player's expected score:
RA and RB are the two ratings. The expected score is between 0 and 1: equal ratings give 0.5 each, and a player rated 200 points higher expects about 0.76.
Then the new rating:
SA is the actual result: 1 for a win, 0.5 for a draw, 0 for a loss. K is the K-factor, which sets how far a single result can move a rating. Custom Elo Games uses 32 for every game and rounds each new rating to a whole number.
A worked example
Player A is rated 1400 and Player B 1200. A's expected score is 1 / (1 + 10−200/400) ≈ 0.76, so B's is about 0.24. If B wins the upset, A loses 32 × 0.76 ≈ 24 points, down to 1376, and B gains the same, up to 1224. If A wins as expected, A gains only 32 × 0.24 ≈ 8, up to 1408.
Frequently asked questions
What does a draw do to Elo?
A draw scores half a point each. Between two equal ratings nothing changes. Otherwise the lower-rated player gains and the higher-rated player loses, because a draw is a better result than the underdog was expected to get.
Why did I gain so few points for a win?
You were expected to win. The bigger the gap between your rating and your opponent's, the less a win is worth to the favourite — and the more a loss costs them.
What rating do new players start at?
On Custom Elo Games everyone starts at 1200. The number itself is arbitrary: what matters is the gaps between players, which grow as results come in.
What K-factor should I use?
A higher K moves ratings faster, which suits a new group whose ratings are still settling. A lower K keeps established ratings steady. 32 is a common choice for casual play, and it's what every game on Custom Elo Games uses.
Does Elo work for more than two players?
This calculator rates one head-to-head. Custom Elo Games also rates free-for-alls of up to 10 players, and team games, by comparing every pair of finishers.
Want this tracked automatically across your whole group?
Custom Elo Games keeps a live leaderboard and rating history for your group — one-on-one, free-for-alls of up to 10 players, or teams.
Sign Up Free