Horse Gestation Period: How Long Is a Horse Pregnant?

How long is a horse pregnant?

A horse carries her foal for an average of 340 days, or about 11 months. Counting from the breeding date, foaling is normal anywhere from day 320 to day 370.

Key checkpoints across the 340-day horse gestation, measured in days from breeding:

Estimate your horse's foaling date

Enter the breeding date for an estimated foaling date at 340 days.

Open the full Horse gestation calculator

Horse gestation stages, month by month

Signs a horse is pregnant

• No return to oestrus about 18 to 21 days after breeding
• Ultrasound confirmation from days 14 to 16
• Udder development starting four to six weeks before foaling
• Waxing of the teats, usually 24 to 48 hours before birth

Signs of approaching foaling

• Relaxed croup muscles and a soft, elongated vulva
• Restlessness, pawing, sweating and repeatedly lying down and getting up in the final hours
• Contact your vet if labour stalls, if the animal strains without progress, or if there is abnormal discharge before foaling begins.

What affects horse gestation length

• Mare gestation is unusually variable: 320 to 370 days is all considered normal, so a single due date is only a midpoint.
• Mares bred in late winter or early spring tend to carry a few days longer than mares bred in summer.
• Colts are commonly carried two to seven days longer than fillies.
• Twin pregnancies are dangerous in horses and are usually reduced to a single embryo at the 14 to 16 day ultrasound.

Horse gestation chart

Every fifth breeding date across the year with the matching foaling date, calculated at 340 days. Find the row closest to the date the horse was served; because normal gestation spans 320 to 370 days, plan for a window of a few days either side. Filter by month, or print the chart for the barn wall or breeding record: navigation, buttons and adverts are hidden on paper.

Sources for horse gestation figures

Figures on this page are drawn from American Association of Equine Practitioners guidance and published equine reproduction data, and checked against the references below. Averages describe healthy animals under normal management; individual animals vary, and nothing here replaces advice from your vet.

• American Association of Equine Practitioners
• Merck Veterinary Manual — reproduction and pregnancy chapters by species
• Penn State Extension — livestock reproduction and breeding management fact sheets
• Oklahoma State University, Breeds of Livestock