Equine pregnancy runs on a longer and less predictable clock than most livestock: about 340 days, or roughly 11 months, from breeding to foaling. This calculator uses that standard gestation length to estimate a mare's due date, show a countdown, and lay out what to expect at each stage — so you can plan ahead for foaling day. This tool is informational only, not a substitute for veterinary advice.
How the Horse Gestation Calculator works
The calculator adds 340 days to the breeding date you enter to produce a headline due date, and also shows an early estimate (320 days) and late estimate (370 days) to represent the normal range of equine gestation. That 320-370 day window is notably wider than most other domestic animals, reflecting the naturally high variability in how long individual mares carry a foal.
Inputs and what they mean
The only input is the breeding date — the day the mare was bred or artificially inseminated. Because equine ovulation timing and gestation length vary more than in most species, treat the calculated due date as the center of a wide, normal window rather than a fixed appointment. A veterinarian can help track the pregnancy more precisely with ultrasound checks, especially early on.
Limits and edge cases
This calculator is a planning tool, not a diagnostic one. It cannot confirm that a mare is actually pregnant, detect twins, or identify complications. Because individual mares vary so much in gestation length, use the result as a wide planning window, and rely on a veterinarian for pregnancy confirmation and for any concerns as the due date approaches.