Equine Pregnancy Calculator
Estimate your mare's foaling date based on the breeding date and equine type.
Standard Horse (340 days)
Pony (335 days)
Donkey (370 days)
Miniature Horse (345 days)
Estimated Foaling Date (Average):
Early Foaling Window (320 days):
Late Foaling Window (370 days):
Note: Most mares foal between 320 and 370 days. A foal born before 300 days is generally considered non-viable, and before 320 days is premature.
Understanding the Equine Gestation Period
Calculating a mare's due date is the first step in preparing for a successful foaling season. Unlike humans, horse gestation is highly variable. While the average length is 340 days, it is perfectly normal for a mare to carry a foal anywhere from 320 to 370 days.
How to Use the Equine Pregnancy Calculator
To use this tool, simply input the last date the mare was bred (or the date of ovulation if known). Select the type of equine, as gestation lengths can vary slightly between standard horses, ponies, and donkeys. The calculator will provide an average due date and the "safe window" for delivery.
Factors Influencing Gestation Length
- Time of Year: Mares bred early in the spring (January-March) tend to have slightly longer gestation periods than those bred in the summer.
- Sex of the Foal: Statistically, colt (male) foals are often carried 2 to 7 days longer than fillies.
- Nutrition: The mare's physical condition and diet can influence the development and timing of the birth.
- Individual History: Many mares are consistent; if a mare carried for 350 days last time, she is likely to do so again.
Signs of Impending Foaling
As the calculated due date approaches, keep a close eye on these physical changes:
- Udder Development: Filling of the udder usually begins 2 to 4 weeks before foaling.
- Teat Waxing: Small beads of colostrum (wax) often appear on the teat ends 24 to 48 hours before birth.
- Muscle Relaxation: The muscles around the tail head and vulva will soften and relax.
- Behavioral Changes: Restlessness, pawing, and looking at the flanks are signs that the first stage of labor has begun.
Example Calculation
If a Standard Horse was bred on May 1st, the average 340-day gestation would result in an estimated due date of April 6th the following year. However, the owner should be prepared for foaling as early as March 17th (320 days) or as late as May 6th (370 days).