Pick the sire’s and the dam’s colors — and any gray, pinto or Appaloosa pattern, or DNA test results you have. You get every color the foal could be, with its odds, from the genes the UC Davis genetics lab tests for. Where a color cannot tell you what a horse carries, the odds are a range, not a guess.
The foal could be
Bay, black or chestnut
Genetics checked 2026-09-26 against the UC Davis Veterinary Genetics Laboratory’s test pages. Odds, not a promise: a foal’s color is one draw from them.
Quick answer: a foal’s color comes from a handful of genes, and it gets one copy of each from each parent. Two chestnuts always make a chestnut. Two palominos make a chestnut 25% of the time, a palomino 50% and a cremello 25%. A bay bred to a chestnut can make a bay, a black or a chestnut. How likely each one is depends on genes a bay does not show, so the honest answer is a range until the bay is tested. Pick both parents’ colors and the calculator lists every color the foal could be, with the odds.
How to use it
Pick the sire’s color and the dam’s. For a gray horse, use the color it was born, or the one on its papers, because gray covers the color underneath over the years. If either parent is gray, tobiano, roan, Appaloosa or frame overo, open the patterns section and tick it. If you have DNA results from a coat color test, put them in too. A test result always wins over the color, and it is what turns a range into an exact figure. The answer shows every foal color with its chance, then the patterns, then anything the genetics lab says you should know about the pairing.
Why some answers are a range
Take a bay. It has at least one copy of E, the gene that lets a horse make black pigment, but it may have one or two. The color looks the same either way. Bred to a chestnut, an E/E bay can never make a chestnut foal, and an E/e bay makes one half the time. So the chance of a chestnut is somewhere from 0 to 50%, and no photograph of the bay can narrow it. A chestnut hides its agouti gene completely, and a smoky black can pass for a plain black. Where the colors cannot say, the calculator works out the least and the most the pairing could give. DNA tests for E, A and cream close the range. The UC Davis Veterinary Genetics Laboratory runs all three from a hair sample.
The genes it uses
It uses eleven genes, each as the UC Davis lab describes it on its own test page. Extension (E) and agouti (A) make the base color: chestnut, bay or black. Cream, dun, champagne and silver dilute it, making palomino, buckskin, grullo, gold champagne and the rest. Gray, tobiano, classic roan, leopard (Appaloosa) and frame overo are patterns laid on top. Each gene is inherited on its own. A parent with one copy passes it to half its foals, and a parent with two copies passes it to every foal. That is the lab’s own rule for every test here, and all the arithmetic follows from it.
What the lab says to watch for
Frame overo is the one that matters most. One copy gives the frame pattern. Two copies give a foal that is born all white with a gut that does not work, and it dies of colic. Breed two frame carriers, and the lab puts that chance at 25%. A frame horse can show very little white, so a horse that looks solid can still carry it. The lab recommends testing Paint Horses, Quarter Horses, Miniature Horses and Thoroughbreds. Two copies of the leopard gene bring night blindness. Silver comes with an eye condition called MCOA, and a chestnut can carry silver without it showing. And the lab says over 70% of gray horses older than 15 develop melanoma. The calculator prints each of these whenever a pairing can produce it.