Select a species, add the traits for each parent, and review the projected outcomes without leaving the page.
Understand how different traits impact your pairings and what the numbers really mean.
Needs two copies to show. An animal carrying a single copy is a het: it looks normal but can pass the gene along.
Example
Het Albino × Het Albino → 25% Albino, 50% het, 25% normal.
One copy is enough to show the full look. Two copies look the same as one, so there is no visibly different super form.
Example
Pinstripe × Normal → 50% Pinstripe, 50% normal.
One copy shows a mid-level version of the trait. Two copies produce a super form with a distinctly stronger look.
Example
Pastel × Pastel → 25% Super Pastel, 50% Pastel, 25% normal.
Why some traits stack cleanly, some combine, and some never show.
Independent genes multiply
Genes on different loci sort independently. A 50% chance of one trait and a 25% chance of another gives a 12.5% (1 in 8) chance of both together.
Allelic genes share a locus
Some genes live at the same spot on the chromosome, like the Mojave, Lesser and Butter group in ball pythons. A parent can pass only one of them, and pairing two produces a combined super form instead of both traits side by side.
Combos build designer morphs
Most named designer morphs are simply several genes expressed in one animal. Stack the genes on each parent and the calculator shows every possible combination and its odds.
Hets can hide for generations
A recessive gene carried as a het never shows until it meets another copy. Normal-looking offspring from a het pairing are labeled as possible hets because the gene may or may not be there.
Some traits are polygenic
Color intensity, pattern reduction and body structure are often controlled by many genes. These line-bred traits improve through selection over generations and cannot be predicted with simple percentages.
What the percentages, fractions and het labels are actually telling you.
Percentages are odds per egg
A 25% result means each individual hatchling has a one-in-four chance of that outcome. It does not guarantee one in every four eggs.
Fractions show the ratio
The fraction beside each percentage (1/4, 3/16 and so on) is the same probability written as a ratio, which is handy when comparing outcomes in one clutch.
Small clutches vary a lot
With only four to eight eggs, real results will swing well away from the maths. Expect the odds to even out across many clutches, not one.
66% and 50% possible hets
When two hets are paired, a normal-looking baby has a two-in-three chance of being het. When a het is paired with a normal, every normal-looking baby has a 50% chance of being het.
Proving out a het
Possible hets are only confirmed by breeding them to a visual or a proven het and producing the visual trait. Until then, treat the label as a probability, not a fact.
How genetics play out in popular species, with a shortcut to the animals currently for sale.
Python regius
The deepest morph library in the hobby, with hundreds of genes across every inheritance type.
Eublepharis macularius
Three separate albino strains plus strong line-bred color work make this a great species to learn on.
Pantherophis guttatus
A textbook recessive species where classic combos come from stacking simple genes.
Pogona vitticeps
A mix of simple recessive genes, one well-known incomplete dominant scale trait and polygenic color.
Heterodon nasicus
A fast-growing morph scene built on a handful of recessives and incomplete dominants.
Boa imperator
Incomplete dominant genes dominate the boa market, alongside two separate albino lines.
Correlophus ciliatus
Mostly polygenic, so most traits are refined by selective breeding rather than predicted by a calculator.
Practical habits that make projects faster and offspring easier to sell.
Research every gene before pairing
A few genes carry known health considerations in their super form or in specific combinations. Check community resources and reputable breeders before committing a pairing.
Keep clear records
Record which genes each parent carries and label possible hets honestly. Good records raise the value of your offspring and protect buyers.
Plan for the long game
Recessive projects usually take two generations to produce visuals. Pair a visual with a het rather than two hets when you can, since it doubles your visual odds.
Sell with the genetics attached
When you list an animal on ReptileAds, add its traits and hets to the listing so buyers can plug it straight into this calculator.
Genetics is more than color. Keep the animals at the center of every pairing.
Know the problem combinations
Some genes are linked to neurological or developmental issues, and a few super forms are not viable. Learn which apply to your species before pairing.
Avoid pairing close relatives repeatedly
Line breeding can lock in a trait quickly, but repeated inbreeding raises the risk of deformities and weak hatchlings. Outcross regularly.
Disclose everything to buyers
List known hets, possible hets and any health considerations on your ReptileAds listing. Transparent breeders build repeat customers.
Breed animals in top condition
Age, weight and body condition matter more than the genes on paper. A healthy pairing produces stronger clutches and better outcomes.
The terms you will see on listings, in breeder chats and in these results.