Enter the mating or egg-setting date and the species to see the likely birth or hatching window — from dogs and cats to cattle, horses and poultry.
Gestation length in animals is a range, not a single number, and the range exists for real biological reasons. In dogs, the spread from 57 to 72 days counted from the mating is mostly because sperm survive for days inside the reproductive tract and ovulation rarely happens on the day of the mating — counted from the LH peak measured by the vet, the same pregnancy is 63 days give or take one. In cattle, breed is the dominant variable: Holstein and Jersey calve around 279 days, while Nelore and other zebu breeds average 292. In horses, the normal range runs from 320 to 370 days, one of the widest of any domestic species, and mares bred late in the season often carry longer. This page shows the average, the early end and the late end, because a calendar that prints only one date teaches the wrong lesson.
Birds are a different mechanism entirely. Incubation is not gestation: what sets the clock is the temperature and humidity of the incubator or of the sitting bird, not the mother's body. A machine running half a degree cold pushes the hatch a day or two later, and a hot one brings it forward. The species and the breed set the baseline — a chicken egg hatches in about 21 days, a duck in 28, an ostrich in 42 — but the incubator is where the variation comes from. The page handles both mammals and birds, with the label and the language switching between "mating" and "eggs set" so the dates make sense.
Two things this tool does not do: it does not diagnose, and it does not replace the veterinarian. A pregnancy that runs past the upper end of the range is a reason to call the vet, not to panic — and a vet following the pregnancy with ultrasound or progesterone timing can narrow the window far more than any table. The gestation periods here come from the Merck Veterinary Manual, Hafez's Reproduction in Farm Animals and Embrapa, the sources a vet would check. Your dates and the result stay in your browser and are never uploaded or stored.
Expected birth date = mating date + average gestation in days. The window runs from mating date + minimum to mating date + maximum. For incubation, the same arithmetic applies from the date the eggs were set.
Because the date of the mating is not the date of fertilisation. Sperm survive for days inside the reproductive tract, and ovulation can happen before or after the mating. Counted from the LH peak — which the vet can measure — the same pregnancy is 63 days, give or take one. The wide range is a mating-date problem, not a gestation-length problem.
Pets: dog, cat, rabbit, guinea pig, hamster, gerbil, mouse, rat, chinchilla, ferret. Livestock: cattle, water buffalo, horse, donkey, pig, sheep, goat, llama, alpaca, camel. Birds (egg incubation): chicken, quail, duck, muscovy duck, turkey, goose, guinea fowl, pigeon, ostrich, cockatiel, budgerigar.
No. Gestation runs inside the mother and depends on her biology. Incubation depends on the temperature and humidity of the incubator or of the sitting bird. A machine running half a degree cold can push the hatch a day or two later, and a hot one brings it forward.
From the Merck Veterinary Manual, Hafez's Reproduction in Farm Animals (7th ed.) and Embrapa — the sources a veterinarian would consult.
Call the vet. A pregnancy that runs long is not automatically an emergency, but it is a reason for a professional check — especially in species where dystocia (difficult birth) is common, such as bulldogs or first-calf heifers.
No. The dates and the result are calculated in JavaScript on your own device. Nothing is uploaded, stored or logged anywhere.
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