The formula, step by step
Take each parent's CombiRank, add them, add 1, divide by 2, and round down. That is the target rank. Find the Pal in the formula pool whose CombiRank is closest to the target. That Pal hatches, unless the pair is a special combo.
Worked example from verified 1.0 data: Penking (2070) + Bushi (1560) = (2070 + 1560 + 1) / 2 = 1815, rounded down. The closest formula-pool Pal is Sibelyx (1810). That is the 1.0 answer, and it is different from the pre-1.0 answer for the same pair.
Special breeding combinations
Special combinations are fixed pairs written into the breeding data. They ignore the formula entirely. Examples verified in the dataset used here include Relaxaurus + Sparkit, Frostallion + Helzephyr, and Starryon + Celesdir. There are 164 special combos in that dataset, including crossover pairs. If your pair is special, no formula calculation will change its result.
One special pair is gender-dependent: Katress + Wixen. Female Katress + male Wixen gives Katress Ignis, and male Katress + female Wixen gives Wixen Noct. That is the only gender-dependent combo in the dataset, and the calculator asks for genders only for that pair.
Can you breed legendaries?
No, not from common parents. Because the formula averages ranks, a child can never be lower-ranked than the lower-ranked parent in a way that jumps to a legendary. Legendaries must be caught first, then bred as a same-species pair for better passives. The same rule applies to raid Pals such as Bellanoir and Bellanoir Libero.
Frequently asked questions
What is CombiRank?
CombiRank is the internal breeding rank for each Pal in the game files. Low ranks are rare Pals, high ranks are common Pals, and the formula averages the parents' ranks.
Do parent genders matter for the formula?
For formula pairs, no — you still need one male and one female in the farm, but swapping which parent is male does not change the species. The only exception is the gender-dependent Katress + Wixen pair.
What happens on a tie?
The calculator picks the closest formula-pool Pal, and on an exact tie it picks the higher CombiRank. The in-game tie handling is not something to rely on for a chain — if your target is a tie, pick a different pair whose average lands cleanly on it.