Coat Colour Genetics Calculator
Estimate likely offspring coat colours using a simple two-locus model (B and E). This is commonly used as a starting point for dogs and other mammals where eumelanin and extension genes are relevant.
What this coat colour calculator does
This calculator predicts offspring coat colour probabilities from two parent genotypes. It uses straightforward Mendelian inheritance at two loci and combines probabilities across all possible gamete pairings. If you are planning a litter, teaching genetics, or just curious about inheritance outcomes, this gives a quick and practical estimate.
Included loci in this model
- B locus: controls black vs brown eumelanin pigment.
- E locus: controls whether eumelanin is expressed in the coat.
In this model, ee is epistatic to the B locus, meaning it can hide black/brown expression and produce a cream/yellow phenotype regardless of BB, Bb, or bb at B.
How to use the calculator
- Select genotype values for Parent 1 at both loci (B and E).
- Select genotype values for Parent 2.
- Click Calculate coat colour probabilities.
- Review both the phenotype percentages and the genotype distribution table.
The phenotype panel tells you what coat colours are most likely. The genotype table is useful if you care about hidden carrier status in future breeding decisions.
How results should be interpreted
Probabilities, not guarantees
Genetics gives expected ratios over many offspring. In small litters, outcomes can vary a lot. A 25% predicted trait may appear zero times or multiple times in one litter simply by chance.
Most likely colour vs full distribution
Many people focus only on the top percentage, but the full distribution matters. For example, if two colours are close (say 37.5% and 31.25%), either could dominate in a small sample.
Important limitations
This calculator intentionally stays simple. Real coat colour genetics can involve additional loci and modifiers, such as dilution, agouti patterning, white spotting, merle, intensity genes, and breed-specific interactions. Environmental effects and age-related coat changes can also alter appearance.
- Does not model pattern genes (brindle, merle, spotting).
- Does not model dilution or silver effects.
- Does not replace DNA testing or professional breeding advice.
Best practices for breeders and owners
If coat colour outcomes are important, combine tools like this with verified pedigree records and genetic testing. Keep careful notes on genotype assumptions and observed offspring. Over time, your own records become extremely valuable for planning and improving prediction accuracy.
Final thoughts
A coat colour calculator is a practical way to turn genotype information into clear expectations. Used correctly, it supports better planning, better communication with buyers or owners, and a stronger understanding of inheritance fundamentals.