MasterTool

Elo Rating Calculator

Calculate expected score and new Elo rating after a game, using the standard Elo expectation and update formulas.

Loading calculator…

What this tool does

Calculate expected score and new Elo rating after a game, using the standard Elo expectation and update formulas. K-factor is set by the governing body (FIDE uses 40 for new players, 20 for most, 10 for established 2400+ players; many online platforms use 32 or less). Ratings are relative to the pool, not absolute skill.

How to use the Elo Rating Calculator

  1. Enter or select your rating.
  2. Enter or select opponent rating.
  3. Enter or select k-factor.
  4. Enter or select your result.
  5. Read the calculated result; change any measurement to compare alternatives.

Formula

expected score = 1 ÷ (1 + 10^((opponent − your rating) ÷ 400)); new rating = rating + K × (actual score − expected score)
rating
Your rating
opp
Opponent rating
k
K-factor
score
Your result

K-factor is set by the governing body (FIDE uses 40 for new players, 20 for most, 10 for established 2400+ players; many online platforms use 32 or less). Ratings are relative to the pool, not absolute skill.

Worked example

For elo rating calculator, the following measurements illustrate the exact method: Your rating: 1600; Opponent rating: 1600; K-factor: 32; Your result: 1.

Inputs

  • Your rating1600
  • Opponent rating1600
  • K-factor32
  • Your resultWin

Result

  • Expected score0.5
  • Rating change16
  • New rating1,616

Results explained

Expected score
Expected score from the formula above. K-factor is set by the governing body (FIDE uses 40 for new players, 20 for most, 10 for established 2400+ players; many online platforms use 32 or less). Ratings are relative to the pool, not absolute skill.
Rating change
Rating change from the formula above. K-factor is set by the governing body (FIDE uses 40 for new players, 20 for most, 10 for established 2400+ players; many online platforms use 32 or less). Ratings are relative to the pool, not absolute skill.
New rating
New rating from the formula above. K-factor is set by the governing body (FIDE uses 40 for new players, 20 for most, 10 for established 2400+ players; many online platforms use 32 or less). Ratings are relative to the pool, not absolute skill.

Frequently asked questions

Exactly 0.5 — the formula is symmetric, so a player rated the same as their opponent is expected to score half a point (a win half the time, or draws on average).

A player rated 400 points higher has an expected score of about 0.909 — they should score roughly 10 points for every 1 the underdog scores. That 10-to-1 ratio is built into the 400-point divisor.

With the same K-factor on both sides, Elo is zero-sum: your gain equals their loss. Different K-factors (for example a new player's 40 vs a veteran's 10) break that symmetry deliberately.

Use your platform's: chess.com and lichess use their own variants (Glicko), FIDE uses 40/20/10 by experience and rating, and many video games hide K inside placement systems. 32 is the classic default.

At most by K points (a total upset with expected score near 0). Routine results between equals move you about half of K — 16 points at K=32 for a win.