Horse Gestation Calculator — Foaling Date Estimator
Enter the date your mare was bred to get her expected foaling date, the normal delivery window (days 320–370), and a live progress bar showing how far along the pregnancy is.
Days until the expected foaling date at 340 days of gestation
- 1
Average gestation period
340Normal range is 320–370 days; 340 days is the standard average. - 2
Days elapsed since breeding
178 - 3
Days remaining = 340 − elapsed
340 − 178 = 162
How does this calculator work?
Horse gestation averages 340 days from breeding to foaling, with a normal range of 320–370 days. Enter the breeding date to get the expected foaling date, the full delivery window, and a progress indicator showing how many days of the average gestation have elapsed.
Formula
How this is calculated
Mare gestation averages 340 days (roughly 11 months), but the normal range spans from about 320 to 370 days. Foals born before day 300 are considered premature and may need intensive care; those born after day 370 are post-term and warrant veterinary monitoring. Breed, individual mare history, season, and nutrition all influence gestation length — Thoroughbreds and Arabians tend toward shorter gestation, while draft breeds and ponies often run longer.
The calculator adds 340 days to the service date to give the expected foaling date, then adds 320 and 370 days for the early and late ends of the normal window. The timeline bar shows gestation progress based on today's date relative to day 340 from breeding.
Use the last confirmed breeding date (or the date of artificial insemination) for the most accurate estimate. If the mare was covered on multiple days, use the last successful cover date. A veterinary ultrasound at 14–16 days post-service is the most reliable way to confirm pregnancy and estimate foaling date.
Frequently asked questions
Between 320 and 370 days is considered normal for most breeds. Foals born before day 300 are premature. The average is 340 days but individual mares often run consistently shorter or longer — keeping records of previous gestation lengths helps predict future ones.
Yes, somewhat. Thoroughbreds and Arabians tend to have slightly shorter gestation (around 330–335 days on average). Draft breeds, ponies, and donkeys often run longer — donkeys average around 365 days. The 340-day figure is a good general starting point for most light horse breeds.
Typical signs within 24–48 hours of foaling include a waxing of the udder (dried colostrum on the teat ends), udder filling and swinging, softening of the muscles around the tailhead, and the mare showing restlessness. Many breeders use foaling alarms or cameras and enlist a vet for mares with known complications.
TG we-Calculate Editorial Team. (2026). Horse Gestation Calculator — Foaling Date Estimator [Online calculator]. TG we-Calculate. https://we-calculate.com/calculator/horse-gestation-calculator
TG we-Calculate Editorial Team. "Horse Gestation Calculator — Foaling Date Estimator." TG we-Calculate. 2026. https://we-calculate.com/calculator/horse-gestation-calculator.
TG we-Calculate Editorial Team, "Horse Gestation Calculator — Foaling Date Estimator," TG we-Calculate, 2026. [Online]. Available: https://we-calculate.com/calculator/horse-gestation-calculator
@misc{wecalculate_horse_gestation_calculator, title = {Horse Gestation Calculator — Foaling Date Estimator}, author = {{TG we-Calculate Editorial Team}}, howpublished = {\url{https://we-calculate.com/calculator/horse-gestation-calculator}}, year = {2026}, note = {TG we-Calculate} }
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