ELO & Progression

How a Game Changes ELO

The Consilium compares the result a player was expected to achieve with the result they actually achieved. Team and Singles games use the same 1.5 multiplier, giving both an effective K-factor of 30.

1. Calculate the Expected Result

For Player A:

Expected A = Score Scale ÷ (1 + 10 ^ ((Player B ELO − Player A ELO) ÷ 400))

The score scale is:

Player B's expected result is the remainder of the scale:

Expected B = Score Scale − Expected A

Equal-rated players are therefore expected to achieve 10–10 in the team system or 50–50 in Singles.

For team 20-point games, the expected result is rounded to a whole team point before the ELO change is calculated. Singles uses the precise expected value internally, although the Results screen also shows a rounded expected result for readability.

2. Determine the Actual ELO Result

Team 20-Point Games

The reported 0–20 game result is used directly. For example, a 17–3 result gives Player A an actual result of 17 and Player B an actual result of 3.

Singles Games

Singles battle scores do not need to add up to 100. The system uses the difference between the two scores and places that margin around a 50–50 centre:

Margin A = Player A Score − Player B Score

The margin is capped between −50 and +50, then converted as follows:

Actual A = 50 + Capped Margin A
Actual B = 50 − Capped Margin A

A margin of 50 or more produces a 100–0 ELO result. Only the margin matters, so 43–45 and 98–100 both produce the same 48–52 ELO result.

3. Calculate the ELO Change

The same formula is used for both scoring systems:

ELO Change = round(
  (Actual Result − Expected Result)
  ÷ Score Scale
  × (20 × 1.5)
)

Because 20 × 1.5 = 30, the shorter form is:

ELO Change = round((Actual Result − Expected Result) ÷ Score Scale × 30)

The final change is stored as a whole number. Exact half-point ties use round-to-even. Singles changes are zero-sum: one player's gain is the other player's loss.

Singles Example: 43–45

Assume both players start on the same ELO, so their expected result is 50–50.

Player 1:

Raw margin = 43 − 45 = −2
Actual ELO result = 50 − 2 = 48
ELO change = round((48 − 50) ÷ 100 × (20 × 1.5))
           = round(−0.6)
           = −1

Player 2:

Raw margin = 45 − 43 = +2
Actual ELO result = 50 + 2 = 52
ELO change = round((52 − 50) ÷ 100 × (20 × 1.5))
           = round(+0.6)
           = +1

The low total score does not increase the rating movement. The two-point winning margin results in a one-point ELO change for equal-rated players.

Team Example: 17–3

Assume both players start on the same ELO, so their expected team result is 10–10.

Player 1:

Actual result = 17
Expected result = 10
ELO change = round((17 − 10) ÷ 20 × (20 × 1.5))
           = round(10.5)
           = +10

Player 2 receives −10 ELO. The exact 10.5 tie rounds to the nearest even whole number, which is 10.

Maximum Change for Equal-Rated Players

For equal-rated players, a maximum result produces:

Team:   round((20 − 10) ÷ 20 × 30)   = +15
Singles: round((100 − 50) ÷ 100 × 30) = +15

Both systems therefore use the same effective K-factor and have the same maximum ±15 ELO movement when the players begin with equal ratings.

Nurgle's Rot (Inactivity Decay)

Starting ELO for New Players

The default ELO for a new or promoted player is the average rating of the bottom 25% of the active player list. Inactive players are excluded before the list is sorted and the bottom quartile is selected, so deactivated players cannot lower the starting ELO calculation.

End-of-Season Reporting