Mare Gestation Calculator
Enter the breeding date to estimate when a mare is due to foal. The default uses an average equine gestation of about 340 days and shows the wide range commonly reported for horses. Treat this as a planning estimate, not a guarantee.
Last updated: September 25, 2026
Frequently asked questions
How long are horses pregnant?
About 340 days on average, roughly 11 months, but the normal range is unusually wide - commonly cited as about 320 to 362 days or more.
Is mare gestation the same as horse gestation?
Yes. A mare is an adult female horse, so mare gestation and horse gestation both refer to equine pregnancy length; this tool covers that single calculation.
Why is the horse gestation range so wide?
Compared to many other livestock species, horses show unusually large individual variation in gestation length, influenced by the mare, breeding season, and the specific pregnancy, without necessarily signaling a problem.
Does the sex of the foal affect gestation length?
Some studies suggest colts are carried marginally longer than fillies on average, though the effect is small relative to overall individual variation.
How early can pregnancy be confirmed in a mare?
Veterinarians can often detect pregnancy by ultrasound around 2 weeks after ovulation, well before any physical signs appear.
How is this different from the Llama or Goat Gestation Calculators?
Each uses a gestation length specific to that species - roughly 340 days for horses, versus about 342 days for llamas/alpacas and about 150 days for goats - and each tool's range reflects that species' typical variation.