Probability is calculated on the ovum rather than the individual; meaning that an individual may potentially be a surrogate mother of a different species, the compatibility is calculated against the ovum to host and the ovum to breeder combined.
The maximum compatible probability is 100%; there are currently no boosters. The order in which probability is calculated and how is as follows, and stacks with each layer: (i.e. calculation for each of the numbered items below (except #4) if the values were 50%, 90%, 150% respectively; the total compatible probability of conception would be the base of 100% multiplied by 50% * 90% * 150% = 67.5% total probability)
Ovum source that is not from the same individual currently hosting the ovum,probability is calculated against the compatibility between species of the ovum and the host; if the species are the same, there would be no variation. (includes a partnered compatibility boost and any permanently forced and transiently forced compatibility at the time the ovum was generated)
Ovum species is calculated against the individual species that is breeding (includes a partnered compatibility boost and any permanently forced and transiently forced compatibility at the time the ovum was generated)
Sum of essence transferred by the breeder over a 5 day period is divided by the total amount of essence the uterus is holding and by the amount that particular species uterus expects (different species have smaller/larger uteruses). (This is the only compatibility calculation which allows a boost up to 200% to offset the previously calculated value; meaning more essence transferred, greater the probability)
| Your Total Essence (over 5 days) | Uterus Total Essence (over 5 days) | Uterus Expect Essence | Efficacy Percent | Conception Probability Factor |
|---|---|---|---|---|
| 15 ML | 15 ML | 30 ML | 100 % | 50 % |
| 15 ML | 20 ML | 30 ML | 75 % | 38 % |
| 45 ML | 45 ML | 30 ML | 100 % | 150 % |
| 45 ML | 60 ML | 30 ML | 75 % | 113 % |
If probability is great enough for conception, the same probability value is checked against any potential hybrids that may be conceived between the two species (ovum and breeder); otherwise, the species will remain that of the ovum source species.