ratings fide calculator

What this FIDE rating calculator does

This tool estimates how your rating changes after a tournament or match series. You provide your current rating, your K-factor, each opponent’s rating, and your game results. The calculator then computes:

• Your total actual score (S)
• Your total expected score (E)
• Your rating change (ΔR)
• Your estimated new rating
• Your performance rating for that event

How FIDE rating changes are calculated

1) Expected score per game

Against each opponent, expected score is:

E = 1 / (1 + 10^{(R_opp − R_you) / 400})

If your rating is much higher, your expected score is closer to 1.0. If it is lower, expected score moves toward 0.0.

2) Event-level score difference

Over all games, we sum expected scores and actual scores:

• S = total actual points (win=1, draw=0.5, loss=0)
• E = total expected points

3) Final rating update

The rating change is:

ΔR = K × (S − E)

Then:

R_new = R_old + ΔR

Choosing the correct K-factor

K controls how fast your rating moves:

• K=40 for newer or developing players in many circumstances.
• K=20 for most established, active players.
• K=10 for experienced, high-rated players with more stable ratings.

Exact eligibility can change with regulations over time, so always verify with current FIDE handbook details for official use.

How to use this calculator correctly

Input format tips

• Opponent ratings can be separated by commas, spaces, or new lines.
• Results can be entered as 1 / 0.5 / 0 or W / D / L.
• The number of results must exactly match the number of opponents.

Interpreting output

• Positive ΔR: you scored above expectation.
• Negative ΔR: you scored below expectation.
• Performance rating summarizes event strength relative to your result rate.

Quick example

Suppose your rating is 1800 (K=20), opponents are 1750, 1820, 1900, and 1780, and results are 1, 0.5, 0, 1. The calculator totals your expected points, compares them with your 2.5/4 score, and outputs your estimated gain or loss.

Important note

This is an educational estimator. Official rating publication can involve additional federation/FIDE processing rules, rounding behavior, eligibility constraints, and event-reporting details. Use this for planning and training, and check official sources for final rated outcomes.