Skip to main content
Sarkari.tools61 calculators for India

FIDE Chess Rating Change Calculator

Calculate expected score and new FIDE Elo rating change after a chess tournament using K-factor (K=10, 20, 40).

Under 30 games, K is always 40.

K-factor for you is 20.

Expected score
1.28
From 3 game(s)
Actual score
1.5
Rating change
+4.3
New rating
1654

How this is calculated

Expected score per game = 1 / (1 + 10^((Ropp − Rplayer) / 400))

ΔR = K × (actual − expected) = 20 × (1.5 − 1.28) = 4.31

K is 40 for the first 30 rated games and for under-18 players rated below 2300, 20 below 2400, and 10 at 2400 and above.

FIDE Chess Rating Change Calculator: how it works

The Elo system adjusts your rating by comparing what you actually scored against what your rating predicted you would score.

Expected score

E = 1 ÷ (1 + 10^((Ropponent − Rplayer) ÷ 400))

E is your expected score, between 0 and 1
A 400-point gap implies roughly a 10 to 1 expectation

Against an equally rated opponent your expected score is 0.5 — a draw. Against someone 200 points higher it is about 0.24, and against someone 400 points higher, about 0.09.

Rating change

ΔR = K × (Actual score − Expected score)

Actual score: 1 for a win, 0.5 for a draw, 0 for a loss

Worked example · Rated 1650, beating a 1720 opponent, K = 20

Given

  • Your rating: 1650
  • Opponent: 1720
  • Result: win
  • K-factor: 20

Working

  1. 1E = 1 ÷ (1 + 10^((1720−1650)÷400))
  2. 2E = 1 ÷ (1 + 10^0.175) = 0.401
  3. 3ΔR = 20 × (1 − 0.401) = +11.98

New rating: 1662

The K-factor

KApplies to
40First 30 rated games, and under-18 players rated below 2300
20Players rated below 2400
10Players who have reached 2400 at any point

Why the system is zero-sum

Whatever you gain, your opponent loses — assuming equal K-factors. Rating points move between players rather than being created, which is what keeps the pool stable over time.

Based on

  • FIDE Rating Regulations

Frequently asked questions

Your expected score against each opponent is computed from the rating difference, then your rating changes by K multiplied by the difference between your actual and expected scores.

More in Academics & Competitive Exams