Horse Coat Color Calculator

Calculator

Sire Genotype

Sire Extension

E allows black pigment. e/e gives chestnut base.

Sire Agouti

A can change black base to bay.

Sire Cream

Cr dilutes many visible coat colors.

Sire Gray

G can make the coat gray over time.

Sire Dun

D adds dun dilution and primitive markings.

Sire Tobiano

To adds a tobiano white pattern label.

Sire Roan

Rn adds a roan pattern label.

Dam Genotype

Dam Extension

Choose the mare red factor genotype.

Dam Agouti

Choose the mare agouti genotype.

Dam Cream

Choose no cream, one cream, or double cream.

Dam Gray

Choose non-gray, gray carrier, or double gray.

Dam Dun

Choose non-dun, dun carrier, or double dun.

Dam Tobiano

Choose tobiano pattern genotype.

Dam Roan

Choose roan pattern genotype.

Example Data Table

Example	Sire genes	Dam genes	Likely learning point
Bay carrier pair	E/e, A/a, N/N, g/g	E/e, A/a, N/N, g/g	Bay, black, and chestnut are possible.
Cream cross	E/e, A/a, N/Cr, g/g	e/e, A/a, N/Cr, g/g	Single and double cream outcomes can appear.
Gray parent	E/E, A/A, N/N, G/g	e/e, a/a, N/N, g/g	Some foals may turn gray over time.

Formula Used

The calculator uses Mendelian inheritance for each selected locus.

Allele chance: each parent passes one allele at each locus.

Genotype chance: sire allele chance × dam allele chance.

Combined chance: Extension × Agouti × Cream × Gray × Dun × Tobiano × Roan.

Outcome chance: matching phenotype combinations are added together.

Base color is read first. Cream and dun are applied next. Roan and tobiano are added as patterns. Gray is shown as a gray overlay when a G allele is present.

How to Use This Calculator

Select the sire genotype for each gene.
Select the dam genotype for each gene.
Press the calculate button.
Read the highest probability outcome first.
Review lower probability outcomes for possible surprises.
Use CSV or PDF export for records.

Use laboratory results when available. Use visual guesses only for rough education.

Horse Coat Color Planning Guide

Why Coat Color Prediction Matters

Horse coat color looks simple at first. It is controlled by many inherited switches. A foal receives one allele from each parent at every locus. Those pairs decide base pigment, dilution, and visible patterns. A calculator helps breeders compare likely outcomes before a mating is planned. It also keeps notes consistent.

Base Color Logic

The first step is the red factor, also called Extension. A horse with two e alleles is chestnut based. A horse with at least one E allele can make black pigment. Agouti then decides where black pigment appears. At least one A allele usually makes bay. Two a alleles with black pigment usually make black. These rules create the common base colors.

Dilution and Pattern Effects

Cream, dun, gray, tobiano, and roan can change the final description. One cream allele can create palomino, buckskin, or smoky black. Two cream alleles can create cremello, perlino, or smoky cream. Dun adds a dilution effect and primitive markings. Gray is dominant and can cover the visible coat over time. Tobiano and roan add pattern labels when present.

Practical Breeding Use

This tool multiplies the inheritance chance for each selected gene. It then groups matching visible outcomes. The final percentages are estimates, not guarantees. Real horses may carry untested genes. Some shades also vary by breed, age, and environment. For serious breeding plans, pair the calculator with laboratory testing. Use the export buttons to save results. Keep those files with mare records, stallion records, and foal notes.

Reading the Result

Start with the highest percentage outcome. Then review rare outcomes. A small percentage can still happen. A zero percent result only means it is impossible under the selected genotypes. Change one parent option to test carrier effects. This is useful when one parent has hidden recessive alleles. The calculator is best for education, planning, and record keeping.

Limitations to Remember

This model assumes the selected genes assort independently. It does not test white spotting groups, champagne, pearl, silver, mushroom, leopard complex, or breed specific modifiers. It also cannot judge shade intensity. A genotype may produce several visual shades. Always confirm unusual results with a qualified equine genetics laboratory before making valuable breeding decisions.

Keep records.

FAQs

1. Is this calculator a genetic test?

No. It is a probability tool. It uses selected genotypes to estimate possible foal coat colors. A laboratory test is still best for confirming hidden alleles and important breeding decisions.

2. Why does chestnut ignore Agouti?

Chestnut horses do not show black body pigment. Agouti changes the placement of black pigment. When the Extension result is e/e, the horse is chestnut based, so Agouti is not visibly expressed.

3. What does gray over another color mean?

It means the foal has a gray allele and an underlying coat color. The horse may be born showing the base color, then lighten with age as gray becomes visible.

4. Can two non-cream parents produce cream?

No, not under this model. A cream foal needs a Cr allele from at least one parent. If both parents are N/N, the calculator gives zero cream outcomes.

5. Why are there many final outcomes?

Several genes are calculated together. Each locus can create multiple genotype results. When modifiers and patterns combine, the final phenotype list can become large.

6. Does roan change the base color?

Roan is treated as a pattern label here. The base coat is still calculated first. The result then adds roan when at least one Rn allele is inherited.

7. Does tobiano guarantee a loud pattern?

No. This calculator only marks the presence of the tobiano genotype. The exact amount and placement of white can vary among individual horses.

8. Why should I export results?

Exports help keep breeding notes organized. CSV is useful for spreadsheets. PDF is useful for sharing simple summaries with owners, clients, or farm records.