Mare foaling date calculator
Mares carry for about 340 days (11 months), and a normal pregnancy can run from about 320 to 370 days. Many mares foal later with a colt and in the spring.
When is my mare due?
A mare bred today (October 4, 2026) is due around September 9, 2027, between August 20 and October 9, 2027.
| Bred | October 4, 2026 |
|---|---|
| Due date | September 9, 2027 (day 340) |
| Normal window | August 20, 2027 to October 9, 2027 (days 320 to 370) |
| Days until foaling | in 340 days |
| Days pregnant today | 0 |
How it is calculated
- Start from the breeding date. Use the last breeding or ovulation date. If the mare was bred more than once, use the last date.
- Add 340 days. The average mare carries for about 340 days, so the due date is 340 days after breeding.
- Mark the normal window. Most foaling happens between day 320 and day 370, so watch from day 320 and call your vet if nothing has happened by day 370.
Buying or selling horses?
Questions
How long is a horse pregnant?
About 340 days on average, roughly 11 months. Anything from about 320 to 370 days is considered normal.
Why is the foaling window so wide?
Gestation length in horses varies with the mare, the season she foals in and the sex of the foal; mares foaling in spring tend to carry longer than those foaling in summer.
When should I call the vet?
Before day 320 a foal is considered premature, so call your vet if the mare shows signs of foaling that early, and for any foaling that stalls after the water breaks.
Sources
The figures are standard published ranges; individual animals vary, so confirm with your veterinarian.
More free tools
- Goat kidding date calculator
- Dog whelping date calculator
- Cat due date calculator
- Rabbit kindling date calculator
- Cow calving date calculator
- Sheep lambing date calculator
- Chicken and duck egg hatch calculator
- Horse hay calculator
- Chicken coop size calculator
- Dog age calculator
Run a farm, club or 4-H site? Put this calculator on your website.