FIDE ELO Rating Calculator

Accurately calculate your chess rating changes after tournaments with precision

Game Inputs

# Player Rating Opponent Rating Score K-factor Rating Change Memo Actions
☰ {{$index + 1}}
{{game.ratingChange > 0 ? '+' : ''}}{{game.ratingChange | number:1}}
Total Rating Change: {{ctrl.totalRatingChange > 0 ? '+' : ''}}{{ctrl.totalRatingChange | number:1}}

K-factor Guidelines

K-factor Values

  • K = 40: For new players until they complete events with at least 30 games
  • K = 40: For players under 18 years old with rating < 2300
  • K = 20: For players with rating < 2400
  • K = 10: For players who have reached 2400+ rating, even if their rating later drops below 2400

Additional Rules (FIDE Handbook chapter 8.3.3)

If the number of games (n) for a player on any list for a rating period multiplied by K exceeds 700, then K shall be the largest whole number such that K × n does not exceed 700.

The rating change is calculated as: Rating Change = K × (Actual Score - Expected Score). The final rating change is rounded to the nearest whole number, with 0.5 rounded away from zero.

How to Use This Calculator

1. Enter Game Information

Fill in your rating in the "Player Rating" field and your opponent's rating in the "Opponent Rating" field for each game. Select the result (Win, Draw, or Loss) and the appropriate K-factor based on the guidelines.

2. Add or Remove Games

Click the "Add Game" button to add more games (up to 11 games total). Use the "✕" button to remove specific games if needed.

3. Save Your Calculations

Enter a name for your calculation in the "Calculation Name" field and click "Save Calculation". This will store your data locally in your browser for future reference.

4. Load or Delete Saved Calculations

Select a previously saved calculation from the dropdown list and click "Load" to retrieve it, or "Delete" to remove it from your saved calculations.

5. Reset the Calculator

Click "Reset Calculator" to clear all input fields and start a new calculation.

Note: All data is stored locally in your browser. No information is sent to any server or external service.

Important FIDE Rating Rules

FIDE Handbook chapter 8.3.1: "A difference in rating of more than 400 points shall be counted for rating purposes as though it were a difference of 400 points."

This means that if the difference between player ratings exceeds 400 points, the calculation uses 400 as the maximum difference to prevent extremely skewed expected scores.

FIDE Handbook chapter 8.3.2: This calculator implements the official FIDE Table 8.1.2 for determining probability scores.

Instead of using the direct formula (1/(1+10^(Rc-R)/400)), this calculator uses the official FIDE probability table based on rating differences. The rating change is calculated as ΔR = K × (Actual Score - Expected Score from table) as specified in the FIDE Handbook.

FIDE Handbook chapter 8.3.4: "The Rating Change for a Rating Period is rounded to the nearest whole number. 0.5 is rounded away from zero."

This means that a rating change of +0.5 is rounded to +1, and a rating change of -0.5 is rounded to -1. The calculator applies this rounding rule to the final rating change.

ELO Changes Calculation Examples

Example 1: Rating Difference > 400 Points (Rule 8.3.1)

Lower Rated Player Wins

  • Player Rating: 1300
  • Opponent Rating: 1800
  • Rating Difference: 500 (capped at 400)
  • Score: 1 (Win)
  • K-factor: 30
  • Expected Score: 0.08 (from table)
  • Rating Change: 30 × (1 - 0.08) = +27.6

Note: Even though the actual difference is 500 points, FIDE rule 8.3.1 caps it at 400 points for calculation purposes.

Higher Rated Player Draws

  • Player Rating: 2050
  • Opponent Rating: 1800
  • Rating Difference: 250
  • Score: 0.5 (Draw)
  • K-factor: 40
  • Expected Score: 0.81 (from table)
  • Rating Change: 40 × (0.5 - 0.81) = -12.4

Example 2: K-factor Adjustment (Rule 8.3.3)

K-factor Adjustment When K×n > 700

When a player plays N = 21 games with a standard K-factor = 40, the product K×n = 40×21 = 840, which exceeds the maximum 700.

According to FIDE Handbook chapter 8.3.3, the K-factor must be adjusted to the largest whole number where K×n ≤ 700.

Kadjusted = ⌊700 ÷ n⌋ = ⌊700 ÷ 21⌋ = ⌊33.33...⌋ = 33

Therefore, for this player, the K-factor would be reduced from 40 to 33 for all games in this rating period. This ensures that K×n = 33×21 = 693, which is below the maximum 700.

Example 3: Rounding Rules (Rule 8.3.4)

Multiple Games with Rounding

FIDE Handbook chapter 8.3.4 states: "The Rating Change for a Rating Period is rounded to the nearest whole number. 0.5 is rounded away from zero."

Let's see how a player's rating changes after playing 2 games:

Game 1:
  • Player Rating: 2000
  • Opponent Rating: 1800
  • Rating Difference: 200
  • Score: 0.5 (Draw)
  • K-factor: 40
  • Expected Score: 0.76 (from table)
  • Rating Change: 40 × (0.5 - 0.76) = -10.4
Game 2:
  • Player Rating: 2000
  • Opponent Rating: 1600
  • Rating Difference: 400
  • Score: 0 (Loss)
  • K-factor: 40
  • Expected Score: 0.92 (from table)
  • Rating Change: 40 × (0 - 0.92) = -36.8
Total Rating Change Calculation:

Game 1 Change + Game 2 Change = -10.4 + (-36.8) = -47.2

According to FIDE Rule 8.3.4, we round to the nearest whole number:

-47.2 rounds to -47

Note: If the fractional part was exactly 0.5, it would round away from zero. For example, -10.5 would round to -11, and +10.5 would round to +11.

Therefore, after these two games, the player's new rating would be: 2000 - 47 = 1953

The Complete Rating Change Formula

ΔR = K × (Sa - Se)

Where:

  • • ΔR = Rating change
  • • K = K-factor (adjusted if K×n > 700)
  • • Sa = Actual score (1 for win, 0.5 for draw, 0 for loss)
  • • Se = Expected score from probability table (based on rating difference, capped at 400)
  • • Se = 1 / (1 + 10(Ro - Rp)/400) (mathematical formula)

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