How does IV inheritance work?

Without a held item, three of the offspring's six IVs are inherited from a randomly chosen parent for each slot and the other three are random. A destiny-knot-style item raises this to five inherited IVs drawn from the two parents, leaving only one random.

How is the perfect-offspring chance computed?

For each inherited slot the offspring takes a perfect IV only if the chosen parent has one. For each random slot the IV is perfect with a 1 in 32 chance. The tool multiplies the per-slot probabilities for all six stats to get the per-egg chance of all six being perfect.

Why does the destiny-knot-style item help so much?

It changes how many slots are inherited from your high-IV parents versus left to pure random chance. Each random slot only has a 1 in 32 chance of being perfect, so reducing the random slots from three to one improves the odds by orders of magnitude.

What does expected eggs mean?

If each egg has probability p of being perfect, the expected number of eggs until your first perfect one is 1 divided by p. It is an average — you may get lucky early or need far more than the expected count.

Do parent natures or moves matter here?

This calculator focuses on IVs, the part that drives stat ceilings. Natures and egg moves are inherited by separate rules and do not change the IV probabilities shown, so they are tracked outside this tool.

Old School RuneScape Breeding & IV Calculator

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Breeding for a flawless specimen is a probability game driven by IV inheritance. This calculator takes your parents’ perfect-IV count and held item and tells you the real chance of a six-IV offspring per egg, plus how many eggs you should expect to hatch.

How it works

Each of the six IV slots is either inherited from a parent or rolled at random. A destiny-knot-style item passes five IVs from the two parents; with none, only three are inherited:

random slot perfect chance = 1 / 32
inherited slot perfect      = parent at that slot is perfect
per-egg perfect chance      = Π over 6 slots of slot-perfect probability
expected eggs               = 1 / per-egg perfect chance

The tool models the inherited slots as drawing from your perfect-IV pool and the remaining slots as independent 1-in-32 rolls.

Example and tips

With five perfect parent IVs and a destiny-knot-style item, five slots are inherited from strong parents and one is a random 1-in-32 roll, giving roughly a 1-in-32 chance per egg and about 32 expected eggs. Drop the item and only three slots are inherited, so three slots must each hit 1-in-32 — the chance collapses to roughly 1 in 32,768. Always breed with the highest-IV parents you can and use the inheritance item; it is the single biggest lever on your egg count.