← Ball Python Morph Pairing Planner
How ball python morph odds work
Every pairing question comes down to the same small piece of arithmetic repeated for each gene. This page shows it for the four kinds of gene the planner handles, with examples it recomputes. It is arithmetic on probabilities, not a promise about any one clutch.
1. Recessive genes (Albino, Clown, Piebald)
A baby needs a copy from each parent to show the trait, and a baby with one copy is a hidden het. Two hets give a quarter visual, half het and a quarter normal. A visual by a het gives half visual and half het.
2. Incomplete dominant genes (Pastel, Enchi, Fire)
One copy shows the trait. Two copies make the Super form. Two pastels give a quarter Super Pastel, half Pastel and a quarter normal; a Super Pastel bred to a normal gives all pastels.
3. Dominant and lethal-when-doubled genes (Pinstripe, Spider)
A dominant looks the same with one or two copies. A lethal one, like spider, loses the double-copy eggs: a quarter of a spider-by-spider clutch does not hatch.
4. Put genes together
Multiply the odds gene by gene. Two pastel het albinos give nine different outcomes: a quarter are Pastel het Albino, one in eight each for het Albino, Pastel, Albino Pastel and Super Pastel het Albino, and one in sixteen each for Normal, Albino, Super Pastel and Albino Super Pastel. The planner does this for every male and female you own, then prices each outcome.
Worked examples
| Pairing | Offspring | Chance per egg |
|---|---|---|
| het Albino × het Albino | het Albino | 50% |
| Normal | 25% | |
| Albino | 25% | |
| Albino × het Albino | het Albino | 50% |
| Albino | 50% | |
| Pastel × Pastel | Pastel | 50% |
| Normal | 25% | |
| Super Pastel | 25% | |
| Spider × Spider | Spider | 50% |
| Normal | 25% | |
| double copy, does not hatch | 25% | |
| Clown × 66% het Clown | het Clown | 67% |
| Clown | 33% | |
| Pastel, het Albino × Pastel, het Albino | Pastel, het Albino | 25% |
| het Albino | 12.50% | |
| Pastel | 12.50% | |
| Albino Pastel | 12.50% | |
| Super Pastel, het Albino | 12.50% | |
| Normal | 6.25% | |
| Albino | 6.25% | |
| Super Pastel | 6.25% | |
| Albino Super Pastel | 6.25% |
A 66% het is treated as passing the gene to a third of eggs. These odds assume independent genes and are not guaranteed for any one clutch.
Common questions
How do you work out ball python morph odds?
Treat every gene as its own site. A recessive gene needs two copies to show, so two hets give 25% visual, 50% het and 25% normal. An incomplete dominant shows with one copy and makes a Super form with two, so two pastels give 25% Super Pastel, 50% Pastel and 25% normal. Multiply the odds of each gene together to get the odds of a combination.
What does it mean that spider is lethal when doubled?
A double copy of the spider gene is reported not to hatch, so a spider-by-spider pairing loses about a quarter of its eggs and the rest are half spider and a quarter normal. The planner takes those eggs out of the expected hatchlings.
Why not pair two genes from the same group?
Genes that sit at the same site on the chromosome, such as the Lesser, Butter and Mojave group, do not follow independent odds, so the simple multiplication gives wrong answers. The planner refuses those pairings rather than guess.