Gecko Morph Calculator: Leopard, Fat Tailed and Crested Geckos

A gecko morph calculator turns a pairing into percentages. You pick a species, choose the traits each parent carries, and the tool multiplies the odds trait by trait. This page explains what those numbers mean for leopard, African fat tailed and crested geckos, and where they stop being reliable.

The guide covers inheritance modes, worked crosses, reading a result and health risks tied to some traits. It links to the full gecko genetics page for the theory.

Using the gecko morph calculator

Select the species first, because each one has its own trait list. Then set each parent to normal, one copy or two copies for every trait, and read the result table.

The tool assumes each trait sits on a separate gene. Treat the output as an estimate, not a guarantee.

The three inheritance modes in the tool

Recessive: the trait shows only when a gecko has two copies. A gecko with one copy looks normal and is called a het, short for heterozygous. Two hets pair to give 25% visual, 50% het and 25% normal per egg.

Incomplete dominant: one copy shows the trait, and two copies show a stronger version that breeders call the super form. The Lemon Frost leopard gecko follows this pattern in a 2021 study of more than 900 geckos, where homozygous animals had more pronounced phenotypes than single copy animals. The causal gene was SPINT1.

Dominant: one copy is enough, and two copies look the same as one. Breeders apply this label to the Enigma leopard gecko, but it is a hobby name, inheritance reported by breeders, not independently tested.

Polygenic and line bred looks, such as most stripes, patterns and color intensity, are not in the tool because no simple ratio describes them. Breeders select for them over generations instead. For color biology in the wider group, see the gecko colors guide.

Worked examples

These crosses show the arithmetic the tool runs. Each row gives the chance for one egg, and each egg is independent of the ones before it.

Two traits on separate genes multiply: the last row combines a 25% albino chance with a 50% Lemon Frost chance, so one egg in eight shows both. A clutch of two eggs does not have to follow these ratios. Four heads in ten coin flips is common, and a small clutch can miss a 25% outcome entirely.

How to read a result

The percentages describe probability for each egg, not a count for the clutch. A 25% outcome means every egg has one chance in four, so a pair can produce none or several from the same clutch.

Het outcomes need proof. A het cannot be told from a normal gecko by eye, so breeders call one “100% het” only when a visual parent is involved, and “possible het” otherwise. Read the label as a probability, not a guarantee.

Sex is not part of the calculation. Leopard and African fat tailed geckos have temperature dependent sex determination, so incubation temperature sets the sex, not a chromosome.

In the African fat tailed gecko, an incubation range of 24 to 28 C mostly gives females, 29 to 30.5 C gives about equal numbers and 31 to 32 C mostly gives males, per Animal Diversity Web. Crested geckos differ: a 2015 sequencing study found ZW sex chromosomes in the species, so their sex is genetic, but the tool still leaves it out.

Traits in the calculator

Each row lists the mode and where the claim comes from. Traits without a paper are labeled as hobby names.

Each of these labels is a hobby name, inheritance reported by breeders, not independently tested, except Lemon Frost. Different breeders sometimes use one name for lines that may not be the same gene, which is another reason to treat the results as estimates. The gecko morph index lists the full set of named looks.

Health linked traits

Some pairings carry a welfare cost that a calculator cannot show. The sourced case is the Lemon Frost. In the 2021 study, over 80% of animals carrying the mutation developed white skin tumors between 6 months and 5 years of age.

A 2020 Scientific Reports case study examined three Lemon Frost leopard geckos aged 10 months to 3 years. All three had nodular lesions that proved to be malignant iridophoroma, a tumor of light reflecting pigment cells. Homozygous geckos in the 2021 colony were viable and fertile, so the super form is not lethal, but it has thickened skin and stronger expression.

These further links are hobby name, inheritance reported by breeders, not independently tested:

• Enigma in leopard geckos: reported with head wobble and circling, called enigma syndrome by breeders.
• Super Lilly White in crested geckos: reported to be lethal, with embryos failing or hatchlings dying.
• Super Cappuccino in crested geckos: reported with nostril and health problems.

Avoid pairings that could give a super form with a reported health problem. A reptile veterinarian can advise on any gecko with lumps, a wobbling head or breathing trouble.

Species calculators

The selector above covers three species, but each has a dedicated tool with more room for its own notes.

• Leopard gecko: the leopard gecko morph calculator holds the longest trait list and the Lemon Frost tumor note.
• Crested gecko: the crested gecko calculator covers incomplete dominant lines and their super forms.
• African fat tailed gecko: the fat tailed gecko calculator has only two recessive traits, both hobby labels.

The wider geckos hub links every species page.

Limits of any gecko genetics calculator

Any gecko morph calculator is only as good as its trait data. Most gecko morphs have no published gene, so the inheritance mode comes from breeding records that no one has independently tested. Only a few, such as the Lemon Frost, have a mapped gene.

Genetics research in geckos is moving. A 2015 study of 12 species found many different sex chromosome systems across the group, and genome projects now exist for the leopard gecko. New papers may confirm or change today’s hobby labels.

Frequently Asked Questions

Can a calculator tell me the sex of the babies?

No. Leopard and African fat tailed geckos set sex by incubation temperature, so parent genes do not decide it. A Punnett square for sex would be wrong for both.

What does het mean on a result?

Het is short for heterozygous. The gecko carries one copy of a recessive trait, looks normal and can pass the trait on. Only a breeding test or a visual parent proves it.

Is a super form always more dangerous than a single copy?

Not always. Lemon Frost homozygous geckos were viable and fertile in the 2021 study. Reported lethal super forms, such as the Super Lilly White in crested geckos, are hobby reports.

Why are so many traits labeled as hobby names?

Few gecko morphs have been tested in a lab. The label marks a claim that comes from breeding records, not from a published genetic study.

Can I combine traits from two different species?

No. The species do not interbreed, and each has its own trait list. The tool runs one species at a time.

Do more eggs improve the odds?

The odds per egg stay the same. More eggs only make the overall ratio closer to the expected one across many clutches.