Over the past two years 30% of MMA bouts ended with an underdog pulling off an upset over the oddsmaker’s favorite. Tapology broke these bouts down by weight class and found a strong correlation between weight division and upset rates. The lighter the fighters are, the more likely there is to be an upset, with a full 7% more bantamweight fights than heavyweight fights being won by an underdog. While it can’t tell you which fights to wager on, it does show that MMA oddsmakers are less capable of predicting what will happen in the smaller divisions.
32% of 135 pound bantamweight and 145 pound featherweight fights end in an upset by the underdog. The upset rate declines with each step up in weight, all the way up to 265 pound heavyweights where upsets only occur 25% of the time. The one notable exception is the 205 pound light heavyweight division, where, strangely, over the past two years there have been more upsets than in any other weight class. Whether this is due to the fighting styles at light heavyweight, the parity of the division or simple randomness is difficult to say.
Despite the 205 pound anomaly, the overall trend is clear: the smaller the fighters, the greater the chance of an upset. Take this into account the next time you are on the fence about going with a bantamweight underdog versus a heavyweight underdog.
| Weight Class | Fight Count | Favorite Won | Underdog Won |
|---|---|---|---|
| Bantamweight – 135 lbs | 34 | 68% | 32% |
| Featherweight – 145 lbs | 74 | 68% | 32% |
| Lightweight – 155 lbs | 187 | 69% | 31% |
| Welterweight – 170 lbs | 127 | 72% | 28% |
| Middleweight – 185 lbs | 146 | 73% | 27% |
| Light Heavyweight – 205 lbs | 85 | 67% | 33% |
| Heavyweight – 265 lbs | 76 | 75% | 25% |
