Chestnut
e/e
Red pigment only. No black anywhere, whatever else the horse carries.
Free foal coat-colour predictor
What colour will your foal be?
Set the sire and dam’s colour genes and see every coat your foal could inherit — with real probabilities, blue-eye and deafness notes, and a lethal-white warning before you breed.
Try
Sire · stallion
Bay
E/e A/a
Base colour
Extension (Red factor)
Agouti
Dilutions
Cream
Dun
Champagne
Silver
Dam · mare
Chestnut
e/e A/a
Base colour
Extension (Red factor)
Agouti
Dilutions
Cream
Dun
Champagne
Silver
Foal outcomes
3 possible colours
Probabilities across all inherited gene combinations.
Chestnut
50%Bay
38%Black
13%No sign-up. Works from the colours you can see or a DNA panel you already have.
The genetics, briefly
A handful of genes paint the whole horse.
01
Two genes set the base
Extension decides whether a horse can make black pigment; Agouti decides where it goes. Between them you get chestnut, bay, or black — every other colour is built on one of these three.
02
Dilutions repaint it
Cream, dun, champagne and silver lighten the base in their own way. One copy of cream turns chestnut to palomino; two copies turn it to cream. The calculator layers each dilution the way pigment actually stacks.
03
One copy or two matters
A horse carries two copies of every gene and passes one at random. That single fact is the whole Punnett square — and why a plain-looking mare can still throw a palomino, a dun, or a paint.
One pairing is not just about colour: crossing two Frame Overo (O/n) carriers risks a lethal white foal. The calculator flags that risk the moment both parents carry it.
Breeders
Plan a mating, weigh your odds of a colour you want, and rule out dangerous carrier pairings before the season starts.
Buyers & owners
Check what a foal’s registration papers claim, or work out what your horse might be carrying under a grey or a pinto pattern.
Students & the curious
See Mendelian inheritance play out on something you can picture. Toggle a gene and watch the whole distribution shift.
Colour guide
Every coat, and the genes behind it.
The same colours the calculator predicts — with the genotype that produces each one, written the way a DNA panel reports it.
Base
Bay
E_ A_
Red-brown body with black points. The most common horse colour worldwide.
Black
E_ a/a
Solid black to the skin. True black stays dark rather than sun-bleaching.
Cream
Palomino
e/e Cr/n
Gold coat, near-white mane and tail. One cream copy on a chestnut.
Buckskin
E_ A_ Cr/n
Tan body with black points. One cream copy on a bay.
Smoky black
E_ a/a Cr/n
One cream on black — subtle, and often mistaken for plain black.
Cremello
e/e Cr/Cr
Pale cream coat, blue eyes, pink skin. Two cream copies on a chestnut.
Perlino
E_ A_ Cr/Cr
Cream body with a faintly warmer mane. Two cream copies on a bay.
Dun
Dun
E_ A_ D/n
Sandy body, black points, dorsal stripe and often leg barring.
Red dun
e/e D/n
Dun dilution on a chestnut, with the same primitive marks.
Grullo
E_ a/a D/n
Smoky mouse-grey with a dark dorsal stripe. Dun on a black base.
Other dilutions
Silver dapple
E_ a/a Z/n
Chocolate body, flaxen mane and tail. Silver dilutes black pigment only.
Gold champagne
e/e Ch/n
Champagne on a chestnut: gold coat, pumpkin skin, amber eyes.
Modifiers
Grey
G/n
Born its true colour, then whitens with age. Grey hides everything beneath it.
Blue roan
E_ a/a Rn/n
A black base ticked evenly with white hairs; head and legs stay solid.
FAQ
Questions breeders ask
How accurate is the calculator?
The colour maths is exact: given the parents’ genotypes, every probability follows directly from Mendelian inheritance. The uncertainty is only in the inputs — if you enter colours by eye rather than a DNA panel, a horse may be carrying a gene that does not show. For breeding decisions, test first.
I don’t have a DNA test. Can I still use it?
Yes. Set each parent to the colour you can see and leave the hidden genes at n/n. You’ll get the outcomes for the genes you know about. Bear in mind chestnuts can secretly carry agouti, and many horses carry cream or dun without obvious signs.
What is the lethal white warning?
Frame Overo (the O allele) is safe with one copy but fatal with two: a foal inheriting O from both parents develops lethal white overo syndrome and dies within days. When both parents carry frame, the calculator shows the exact risk so you can avoid the pairing or test the foal’s genotype.
Why does grey override every other colour?
Grey is progressive depigmentation. A grey foal is born its genetic colour — bay, chestnut, whatever — and slowly turns white over years. The horse still carries and passes on its base colour, which is why two greys can produce a non-grey foal.
Which genes does it cover?
Extension and Agouti for the base; Cream, Dun, Champagne and Silver for dilutions; Grey and Roan as modifiers; and Tobiano, Frame Overo, Splashed White and Sabino 1 for white patterns — twelve loci in total.
Is it really free?
Yes — the calculator is free and needs no account. It runs entirely in your browser, so nothing about your horses is sent anywhere.