absurdtools

Elo Rating Calculator

Work out what a game or a whole event does to your rating, with the right K-factor applied and a performance rating that is not the crude one.

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Rating change
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New rating
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Expected score

What the number means

2700+ Super-grandmaster Not an official title. About forty players in the world are here at any time.
2500+ Grandmaster The GM rating requirement. Norms are needed as well as the number.
2400+ International Master The IM rating requirement, and where the elite K-factor of 10 kicks in for good.
2300+ FIDE Master The FM rating requirement. No norms needed — the rating alone earns it.
2200+ Candidate Master The usual threshold for the CM title, and where "master" starts being used.
2000+ Expert Beats most club players consistently. Preparation begins to matter.
1800+ Class A Strong club player. Punishes an inaccuracy rather than waiting for a blunder.
1600+ Class B Plans rather than moves. Endgames start being won on technique.
1400+ Class C Opening principles are habit rather than rules being followed.
1200+ Class D Basic tactics — forks, pins, back-rank mates — are seen most of the time.
1000+ Novice Sees one-move threats reliably and has stopped losing pieces for nothing.
0+ Beginner Knows the moves. Games are decided by whoever hangs less material.

Things worth knowing

  • A rating difference gives an expected SCORE, not a chance of winning. Draws mean 0.76 out of 1 can be three wins and a loss, or two wins and two draws, and the rating cannot tell them apart.
  • The K-factor is not one number. FIDE uses 40 until you have thirty rated games, 20 after that, and 10 once you have ever reached 2400 — and that last one is permanent, even if your rating drops back.
  • Ratings are zero-sum between two players on the same K-factor: whatever one gains, the other loses. On different K-factors they are not, which is how points enter and leave the pool.
  • A performance rating from a single event is a very noisy number. Over five games the margin of error is wider than most of the rating classes below.
  • Different federations run different pools. A USCF rating and a FIDE rating are not the same scale and should not be compared directly.

How to use

  1. Enter your rating and how many rated games you have played.
  2. Add an opponent and a result, or a whole event’s opponents and your score.
  3. The K-factor is worked out for you from the FIDE rules.

Frequently asked questions

What is the K-factor and why does it change?

It is the multiplier that decides how much one game moves you, and it is not a single number. FIDE uses 40 until you have played thirty rated games, 20 after that, and 10 once you have ever reached 2400. That last one is permanent: dropping back below 2400 does not give you K=20 again, which is the part people are most often surprised by.

Is the expected score my chance of winning?

No, and the difference matters. It is the share of the POINTS you would be expected to take, and draws are half a point. A 200-point favourite is expected to score 0.76 out of 1, which could be three wins and a loss or two wins and two draws — the rating cannot tell them apart.

Why does beating a much weaker player gain almost nothing?

Because you were expected to. The change is the K-factor multiplied by the gap between what you scored and what you were expected to score, so a result that surprises nobody moves nothing. The flip side is that losing that game costs you almost the whole K-factor.

Which performance rating is right?

The one shown first: the rating whose expected score against that exact field equals what you actually scored, found by search. The familiar average-plus-400-per-win formula is shown alongside because it is widely used, but it breaks down at a clean sweep — it says you performed exactly 400 above the field, which is a convention rather than a measurement.

Are ratings zero-sum?

Between two players on the same K-factor, yes — whatever one gains the other loses exactly. When the two are on different K-factors they are not, and that is how points enter and leave the pool over time.

Can I compare a FIDE rating with a USCF one?

Not directly. They are separate pools with their own histories and their own K-factor rules, so the same player usually carries different numbers in each. The classes here are rough bands rather than an official conversion.

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