Enter a mare's breeding date for the foaling due date — or reverse it and enter the foal's birth date to find the breeding window.
A mare's gestation averages about 340 days — roughly 11 months. A healthy foal can normally arrive anywhere from 320 to 370 days after breeding, so 340 days is the average, not an exact deadline. This calculator adds 340 days to the breeding date for the expected foaling date, with a likely window of 331–346 days.
Already have a foal on the ground? Switch to reverse mode and enter the birth date. The calculator subtracts about 340 days to estimate the breeding date and shows a breeding window — useful for working out the likely covering date and which stallion was the sire.
Gestation varies by mare, breed, and season, so treat this as a general estimate for information, not veterinary advice — a vet monitoring your mare gives the most accurate timeline. Source: average equine gestation ~340 days (320–370 day range) as used by equine veterinary and breeding references.