Mare Gestation Calculator

Are you wondering when your pregnant mare will foal? Use our Mare Gestation Calculator to find out! The average horse gestation length ranges from 320 to 370 days; most mares will foal within 330 to 345 days of successful breeding. However, mares have successfully foaled with gestation lengths outside this range.

Please Note: The Horse Illustrated Mare Gestation Calculator is intended for use only as a foaling calculator tool for horses. It does not consider differences between individual mares.

Horse Illustrated is not responsible for problems or injuries arising from the use/misuse of this gestation calculator tool or for any inaccuracy in the foaling date estimate of an individual horse.

What date was the mare bred?

Estimated foaling date:

Select a date to see the estimate.

Horse Breed Gestation Table

Breed	Average Gestation Period (Days)	Range (Days)
Thoroughbred	340	320–360
Arabian	340	315–365
Quarter Horse	340	320–360
American Paint Horse	340	320–360
Appaloosa	340	320–360
Morgan	340	330–350
Tennessee Walking Horse	340	320–360
Standardbred	340	330–350
Warmbloods (Dutch, Hanoverian, etc.)	345	330–360
Draft Horses (Clydesdale, Shire, Percheron)	345	330–360
Shetland Pony	335	320–350
Welsh Pony	330	320–345
Miniature Horse	330	320–345
Mustang	340	320–360
Icelandic Horse	340	330–360

Note:

This calculator gives a gestation range of 331-346 days from breeding (adding a day for ovulation to a 330- to 345-day range).
Individual mares tend to have their own gestation length tendencies.
Ponies, on average, tend to have shorter horse gestation periods than full-size horses.
This calculator is not intended for gestation estimation in donkeys or other equids—only horses.

FAQ

How long is horse's gestation period or length?

The gestation period for a horse is approximately 340 days, or about 11 months on average. Some mares may give birth earlier or later.

What is a mare horse?

A mare is an adult female horse or other equine. Typically, a mare is a female horse over the age of three, while a filly is a female horse three years old or younger.

What is a horse calculator?

A "horse calculator" is a tool—often an online calculator or app—used to estimate a horse's weight, feed requirements, or possible coat color outcomes based on factors such as measurements, breed, and parental information.