Pick the parents
For each parent, pick the status on each trait. Normal, visual, het carrier, or homozygous, depending on the dominance pattern. The dropdowns hide options that do not apply.
Free tool · 03 · Morph Calculator
What will the
clutch look like?
Run a Punnett-square prediction on a proposed crested gecko pairing. Six traits with confirmed Mendelian genetics: Lilly White (incomplete dominant, lethal when homozygous), Axanthic and Phantom (recessive), Dalmatian, Pinstripe, and Hypo (dominant). The polygenic stuff is documented in the prose, not faked in the math.
Free · no signup~2 minutesCrested geckos
Incomplete DominantRecessiveDominant
Need traits this tool does not cover?Open the complete 30+ allele calculator on ReptiDex
How it works
Three steps,
confirmed genetics.
The calculator runs each trait as its own independent Punnett square based on the dominance pattern. Results assume the parental genotype you typed in is correct. The lethal warning for Super Lilly White is hard-coded, not derived.
Run the math
Each trait gets an independent Punnett square. The engine encodes the published dominance patterns from the ReptiDex genetics research database, including the Lilly White lethal-homozygous case.
Read the distribution
Each trait card shows the offspring distribution and a one-line note on what each outcome means in plain English. The lethal cases get an explicit flag in red.
For multi-species and combo morphs
ReptiDex covers what
this tool cannot.
This calculator covers six crested gecko traits with hard-coded Mendelian logic. ReptiDex extends that to multiple reptile species, combo morph predictions, an AI morph identifier, and a full genetics reference library. Built by the same breeder.
Common questions
A few things people
ask about gecko genetics.
Lilly White is an incomplete dominant. One copy produces the visible Lilly White phenotype. Two copies (Super) are lethal. Offspring hatch but typically die within the first week with breathing difficulty, motor deficits, and inability to eat. This is distinct from a recessive lethal that kills in the egg. The calculator surfaces the warning so the breeder makes an informed call before the pairing.
Only the six traits with confirmed Mendelian genetics are calculated here: Lilly White, Axanthic, Phantom, Dalmatian, Pinstripe, and Hypo. Base color intensity, Harlequin and Flame pattern type, White Pattern, Orange Pattern, and Dalmatian spot density beyond the dominant switch are polygenic and not fully mapped. The page documents them in the prose so the gaps are visible.
This tool covers six crested-gecko traits with hard-coded Punnett-square logic. The ReptiDex calculator supports multiple reptile species, combo morph predictions, an AI morph identifier, and a full genetics reference library, all built by the same breeder. Most working programs use the BBD tool for quick checks and ReptiDex for multi-species programs and deeper combos.
A visually expressing dominant animal could be carrying one copy (heterozygous) or two (homozygous). Without a test pairing, you cannot tell which from looking. The calculator treats the unconfirmed case as heterozygous because that is the more conservative prediction. Confirm with a test pairing if the answer matters for the next season's plan.
Sable (SA) and Cappuccino (CAPP) are the first confirmed allelic complex in crested geckos. Both alleles sit at the same locus. Crossing SA × CAPP produces a Luwak phenotype (intermediate). The cross cannot produce an animal that is homozygous for both, which is the breeding-test evidence that proved the shared locus. The calculator does not model this yet because predicting it requires confirming the underlying genotypes through pairings, not from phenotype alone.
Not yet. The /tools page-wide email-save flow ports in a follow-up ticket so each free tool's result lands in your inbox. Until then, screenshots work and the URL holds the page state if you stay on the same browser session.
Tracking pairings, hatches, and outcomes?
The custom records app extends this kind of genetics work into a full per-program tool. Pairings, clutches, hatch tracking, weight curves, and predictions trained against the outcomes from your own line, not a generic database.
See the records app