The mechanics behind the egg.

The standard formula

Every pal carries a hidden number the community calls its breeding rank (also "CombiRank" or "breeding power"). It has nothing to do with level, stats, or the label on its status screen — it exists purely to decide what an egg turns into. Lower numbers sit at the top: rare, powerful pals. Higher numbers are the common pasture fodder you catch in the first hour.

Put a male and female pal of any two species into a Breeding Farm with a cake, and the game averages their ranks:

Whichever formula-eligible pal has a breeding rank closest to that number is what hatches. If two species are exactly equidistant, the game breaks the tie toward the lower index number. This is also why the result is never rarer than either parent — the average can't fall outside the range you started with.

Three ways the formula gets overridden

• Same species: two of the same pal always produce that pal, no averaging involved.
• Fixed combos: a specific list of exact pairings — usually elemental variants like a Cryst, Noct, Aqua, or Ignis form — that always produce a set result regardless of rank. Full list below.
• Same-species-only pals: a handful of pals (mostly late-game and legendary) can never be reached through the averaging formula at all — only by breeding two of themselves, or via one of the fixed combos below.

Fixed combo reference

These override the formula completely — if your pair matches one of these, this is what you get, no averaging involved.

Mutations

Mutation is a separate roll layered on top of every egg, not a different formula. Base odds are 1% per egg; an Extravagant Vegetable Cake raises that to 3%. A mutated egg always hatches into something notably rarer than the pair's standard result, guaranteed Alpha, at Condensation Level 2, with four passive skills — at least two of them Tier 4, and one guaranteed to be a mutation-exclusive passive (Babysitter, Heavily Armored, Idiosyncratic, Immortality, or Skymarcher). See the mutation calculator for a cake-by-cake breakdown.

Passing down passives and active skills

Breeding also rolls for which passive skills and active skill carry over from the parents to the egg — species is only half the picture. A Special Cake improves the odds a passive skill transfers. Passive and skill inheritance is randomized per-egg and isn't something a calculator can pin down in advance, so Hatchlog focuses on predicting species and leaves skill rolls to the game.

Working toward a target, step by step

1. 1

   Look up your target's breeding rank on the Pal database.

2. 2

   Already own a pal you'd like to build from? Use Breeding Path to search forward.

3. 3

   Starting from the target instead? Use Breeding Tree to explore parent pairings backward, generation by generation.

4. 4

   Check the fixed combo list above first if your target is a Cryst/Noct/Aqua/Ignis variant — it's usually faster than laddering through ranks.