How ratings work

Elo calculation

Keiko League uses an Elo-style rating. Your rating changes only after both athletes submit matching results for the same QR session.

For each athlete:

• Expected score = 1 / (1 + 10 ^ ((opponent_rating - current_rating) / 400))
• Actual score = 1 for a win, 0 for a loss
• K-factor = 32
• Delta = round(K * (actual_score - expected_score))
• New rating = current_rating + delta

Quick example: if you beat a higher-rated athlete, your expected score is lower, so your rating gain is usually bigger. If you lose to a lower-rated athlete, your drop is usually bigger.

We also show rating reliability as rated-bout count beside Elo. Leaderboard rank additionally applies activity-based recency adjustments for inactive athletes.

Source of truth: EloCalculator, RecordBout, and ConfirmQrSessionReport in the Rails app.