Søndags CS

ELO?

How ELO Works

Starting ELO

Every player starts at 1000 ELO. Your ELO changes after every match based on the outcome.

Gaining ELO

You gain ELO by winning matches. The amount you gain depends on the relative strength of both teams:

  • Beating a higher-rated team gives you more ELO (upset bonus).
  • Beating a lower-rated team gives you less ELO (expected win).
  • Winning with fewer players than the opponent gives bonus ELO.
Losing ELO

You lose ELO when your team loses. The same factors apply in reverse:

  • Losing to a lower-rated team costs you more ELO (unexpected loss).
  • Losing to a higher-rated team costs you less ELO (expected loss).
Examples

Equal teams

Win: +16 / Loss: -16

Favored team wins

Win: +3 / Loss: -29

Underdog wins

Win: +29 / Loss: -3

The Formula

The system uses a K-factor of 32 and adjusts for team size imbalances. All players on the winning team gain the same ELO, and all players on the losing team lose the same ELO.

1. Team size adjustment

When teams are uneven, an adjustment is applied based on the ratio of team sizes:

sizeAdj = 200 × log₂(winnerCount / loserCount)

This adjustment is added to the winner's ELO and subtracted from the loser's for the calculation.

2. Expected outcome

The expected win probability is calculated using the standard ELO formula:

E(winner) = 1 / (1 + 10^((adjLoser − adjWinner) / 400))

A 400-point difference means the stronger team is expected to win ~91% of the time.

3. ELO change

The actual ELO change is proportional to how unexpected the result was:

winnerΔ = round(32 × (1 − E(winner)))
loserΔ = round(32 × (0 − E(loser)))

The K-factor of 32 controls the maximum ELO swing per match. An upset win can earn up to +32, while an expected win earns as little as +1.

Levels

Your level is based on your ELO. Everyone starts at Level 5 (1000 ELO).

1
0 – 499
2
500 – 749
3
750 – 899
4
900 – 1050
5
1051 – 1200
6
1201 – 1350
7
1351 – 1530
8
1531 – 1749
9
1750 – 2000
10
2001+