Horse Coat Color Calculator
Estimate a foal's possible coat color from sire and dam genotypes for Extension, Agouti, Cream, and Gray.
Foal color probability calculator
This horse coat color calculator estimates likely foal colors by crossing the selected parent genotypes. It models four common loci: Extension for red or black pigment, Agouti for bay or black distribution, Cream for dilution, and Gray as a dominant modifier.
A horse coat color calculator predicts foal coat colors from parent genetics. Enter the sire and dam's base color genes, dilution genes, gray gene, and any known pattern genes as part of your breeding notes. The calculator estimates color probabilities, but DNA testing gives the most reliable parent gene data.
Results are probabilities, not guarantees. A real horse coat can also be changed by dun, roan, champagne, pearl, silver, white spotting, leopard complex, flaxen, sooty shading, and other genetic or visual modifiers.
Most likely foal color
Probability -- from -- genotype combinations.
Red base chance
--
Foal is e/e at Extension.
Black pigment chance
--
Foal has at least one E allele.
Cream dilution chance
--
Foal receives at least one Cr allele.
Gray modifier chance
--
Foal has at least one G allele.
Ranked coat color probabilities
| Coat color result | Probability | How to read it |
|---|
Note: Gray is shown as a modifier over the likely birth color because many gray horses are born bay, black, chestnut, palomino, buckskin, or another base color before progressive lightening.
How to use the horse coat color calculator
- Select the sire and dam Extension genotypes: E allows black pigment, while e/e creates a red base such as chestnut or sorrel.
- Choose Agouti for each parent: Agouti affects horses with black pigment by restricting black to the points, which creates bay. Without dominant Agouti, a black-pigment foal can be black.
- Add Cream dilution: One Cr allele can produce palomino, buckskin, or smoky black. Two Cr alleles can produce cremello, perlino, or smoky cream.
- Set Gray status: A foal with at least one G allele is expected to gray over time, even when its birth coat has another base color.
- Compare the ranked results: The table shows the calculated probability for each possible color outcome from the selected parent genotypes.
How the coat color calculation works
The calculator creates a simple Punnett-style cross for each gene. Each parent passes one allele at each locus, so a heterozygous parent such as E/e has a 50% chance of passing E and a 50% chance of passing e.
Extension is evaluated first because e/e prevents black pigment in the coat and produces a chestnut or sorrel base. If the foal has E/E or E/e, Agouti decides whether black pigment is distributed as bay or remains black across the body.
Cream and Gray are then applied as modifiers. Cream changes the base color depending on whether the foal receives zero, one, or two Cr alleles, while Gray can gradually lighten any base color.
Foal probability = Extension cross x Agouti cross x Cream cross x Gray cross
Base color = Extension result + visible Agouti result
Final color = base color + Cream dilution + Gray modifier
Genetics references: UC Davis VGL equine coat color genetics and UC Davis VGL Red Factor and Agouti panel.
Core genes included in this calculator
| Gene / locus | Common notation | What it affects | Visible result |
|---|---|---|---|
| Extension / MC1R | E or e | Controls whether black pigment can be produced. | e/e produces chestnut or sorrel; E/_ allows black pigment. |
| Agouti / ASIP | A or a | Controls distribution of black pigment. | A/_ on a black-pigment base produces bay; a/a can produce black. |
| Cream / SLC45A2 | N or Cr | Dilutes red and black pigment. | One copy can make palomino or buckskin; two copies create double-dilute colors. |
| Gray | G or g | Progressive depigmentation of hair. | G/_ can gray over any base color with age. |
Additional reading: University of Illinois College of Veterinary Medicine on horse coat color.
Base color genotype lookup
Use this lookup when you already know the Extension and Agouti results from a DNA test. It explains why some horses carry an allele that does not match the visible coat color.
| Extension genotype | Agouti genotype | Visible base color | Breeding note |
|---|---|---|---|
| e/e | A/A, A/a, or a/a | Chestnut or sorrel | Agouti can be hidden because the horse does not produce black coat pigment. |
| E/E or E/e | A/A or A/a | Bay | Black pigment is restricted to the points, such as mane, tail, legs, and ear rims. |
| E/E or E/e | a/a | Black | No dominant Agouti allele is present to restrict black pigment to the points. |
What the result can and cannot tell you
A coat color result is easiest to interpret when both parents have been genetically tested. Visual color alone can be misleading because a gray horse may hide its original base color, and smoky black or subtle cream dilution can look similar to non-dilute black.
Probability, not certainty
A 25% result does not mean every fourth foal will have that color. It means each pregnancy has that probability under the selected genotypes.
Hidden genes matter
A horse can carry recessive alleles without showing them. Testing helps confirm whether a parent is homozygous or heterozygous at important loci.
Patterns are separate
White markings, tobiano, frame overo, sabino, splashed white, leopard complex, and roan are not included in the base color result.
Input quality checklist before you trust the percentages
The calculator is only as reliable as the sire and dam genotype data you enter. Before using the result for a breeding plan, sale listing, registration note, or foal color discussion, check these common weak points.
Confirm hidden alleles
A chestnut horse can hide Agouti, and a bay horse may or may not carry the recessive a allele. DNA testing is the cleanest way to separate homozygous from heterozygous parents.
Be careful with gray horses
A mature gray horse may no longer show its birth color. If old photos or test results are unavailable, the underlying Extension, Agouti, and Cream status may be guessed incorrectly.
Separate base color from patterns
Tobiano, overo, sabino, splash, roan, and leopard complex can change the visible coat dramatically, but they do not replace the base color calculation.
Record dilution genes clearly
Cream, dun, champagne, pearl, and silver can create similar-looking phenotypes in some horses. Use test names and genotypes, not just a color description, when accuracy matters.
When genetic testing is worth it
Genetic testing is most useful when the breeding decision depends on a specific outcome, when a parent is gray and the base color is uncertain, or when a horse's phenotype does not clearly show whether it carries Cream, Agouti, or Extension.
Testing also helps when you need to avoid or plan for linked color traits, pattern genes, or breed registry requirements. A lab report can identify alleles that a visual inspection cannot reliably separate.
Good time to test
Before breeding, selling a color prospect, or registering a color-specific foal.
Calculator use
Use confirmed genotypes when possible for cleaner probability estimates.
Example parent crosses and expected probabilities
These examples show how a single hidden allele can change the foal color distribution. Use them as a quick comparison when checking whether your calculator result is plausible.
| Parent cross | Key genotype idea | Expected result pattern |
|---|---|---|
| Chestnut x chestnut | Both parents are e/e at Extension. | Foal base color is red/chestnut unless another dilution or modifier changes the appearance. |
| Bay E/e A/a x bay E/e A/a | Both parents carry red and black-distribution alleles. | Bay is common, but black and chestnut are both possible from recessive allele combinations. |
| Palomino N/Cr x chestnut N/N | One parent can pass Cream, and both are red-base examples. | Foals are usually split between chestnut and palomino when no other modifier is present. |
| Gray G/g x non-gray g/g | One parent has one dominant Gray allele. | Each foal has about a 50% chance to inherit Gray over its underlying birth color. |
Common color scenarios
Two chestnut parents
Two e/e parents can only pass e at Extension, so the foal will have a red base. Cream, Gray, and pattern genes can still modify how that red base appears.
Bay crossed with black
The foal may be bay, black, or chestnut depending on whether each parent carries e and whether the bay parent passes A or a at Agouti.
One gray parent
A G/g gray parent has a 50% chance of passing Gray. A G/G gray parent is expected to pass Gray to every foal.
Single cream parent
A N/Cr parent has a 50% chance of passing Cream. The visible result depends on whether the foal's base is chestnut, bay, or black.
Interesting fact
Gray is more than a visual coat color modifier because it is also linked with age-related skin changes in horses. The University of Minnesota College of Veterinary Medicine reports that melanoma incidence reaches about 80% in gray horses older than 15 years. That statistic does not change a foal color probability, but it explains why knowing whether the gray gene is present can matter beyond appearance. Source: University of Minnesota College of Veterinary Medicine.
Frequently Asked Questions
What does a horse coat color calculator do with sire and dam genetics?
A horse coat color calculator estimates possible foal coat colors by combining sire and dam genotype data in a Punnett square style calculation. It uses inheritance rules for the extension gene, agouti gene, cream gene, and gray gene, then turns each allele combination into a visible phenotype and probability result.
Why does the agouti gene not change a chestnut horse phenotype?
The agouti gene controls where black pigment appears, so it is visible only when the horse has at least one E allele at the extension gene. A chestnut horse is e/e and does not produce black coat pigment, so the agouti genotype can be hidden visually while still being passed to a foal.
Can this calculator predict cream dilution colors like palomino or buckskin?
Yes, when cream gene genotypes are entered. A chestnut base with one Cream allele is shown as palomino, while a bay base with one Cream allele is shown as buckskin. Double-cream dilution combinations are also included as cremello, perlino, and smoky cream, with each result shown as a probability.
Why is the gray gene listed as a modifier over another coat color?
The gray gene is treated as a modifier rather than a separate base color in this model. A foal may be born bay, black, chestnut, buckskin, palomino, or another color phenotype and then become progressively lighter if it inherited a dominant Gray allele.
Does the calculator include dun, roan, champagne, silver, pearl, or white pattern genes?
No. This calculator focuses on four widely used inputs so the result stays readable. A dun gene, roan gene, champagne gene, silver gene, pearl gene, tobiano gene, overo gene, sabino gene, splash gene, leopard complex, and other pattern or dilution genes require a more detailed genetic panel or DNA test.
Can two non-gray horses have a gray foal?
In the simple dominant gray gene inheritance model used here, two g/g parents cannot produce a gray foal because neither parent has a G allele to pass. If a horse's gray genotype is uncertain, a DNA test is the safer input than visual identification, especially when age or coat color changes make the phenotype hard to read.
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Disclaimer: This horse coat color calculator is for general educational and informational use only. It is not a veterinary, breeding, genetic counseling, laboratory, registry, purchase, sale, insurance, or professional advisory tool. Results are simplified estimates based only on the selected genotypes for Extension, Agouti, Cream, and Gray, and they may not reflect the complete genetic profile, phenotype, health status, ancestry, breed rules, or registration requirements of any individual horse. Coat color expression can be affected by additional genes, incomplete information, testing limitations, sample quality, record errors, visual misidentification, age-related color change, and environmental presentation. For breeding decisions, medical questions, breed registration, genetic disease screening, or financially important transactions, consult a qualified veterinarian, equine genetic testing laboratory, breed registry, or other appropriate professional.
Last updated: May 17, 2026