Free tool
Mare Gestation Calculator
Enter the breeding date below to get the expected foaling date and every veterinary milestone of the 340-day equine pregnancy.
Expected foaling date
Tue, October 19, 2027
Foaling window: Wed, September 29, 2027 → Thu, November 18, 2027
Veterinary milestone schedule
Based on a 340-day gestation. Always confirm with your veterinarian.
First ultrasound
Fri, November 27, 2026 · day 14
Confirm pregnancy and rule out twins.
Heartbeat scan
Fri, December 11, 2026 · day 28
Confirm fetal heartbeat.
Endometrial cup formation
Mon, December 28, 2026 · day 45
Pregnancy is more stable from this point.
Sex determination scan
Tue, January 12, 2027 · day 60
Optional — fetal sex can be identified by ultrasound.
EHV-1 vaccine (month 5)
Mon, April 12, 2027 · day 150
Rhinopneumonitis booster to prevent abortion.
EHV-1 vaccine (month 7)
Fri, June 11, 2027 · day 210
Second rhinopneumonitis booster.
EHV-1 vaccine (month 9)
Tue, August 10, 2027 · day 270
Third rhinopneumonitis booster.
Rotavirus + pre-foaling vaccines
Thu, September 9, 2027 · day 300
Boost antibodies passed via colostrum to the foal.
Foaling window opens
Wed, September 29, 2027 · day 320
Move mare to foaling stall, monitor udder.
Expected foaling date
Tue, October 19, 2027 · day 340
Average gestation length for horses.
Foaling window closes
Thu, November 18, 2027 · day 370
Beyond this, consult your vet.
Keep every covering on record
NexxorFarm logs every covering — mare, stallion, method, result and cost — and shows your pregnancy rate. Add each vet milestone above as a vet record with a due date and it appears on your in-app reminders list. Gestation tracking with an expected foaling date is in preparation.
Start free — up to 2 animalsHow long are horses pregnant?
The average horse gestation period is 340 days (about 11 months and 7 days). Normal foaling can happen anywhere between 320 and 370 days from the date of conception. Maiden mares, mares carrying colt foals, and pregnancies that start in late spring tend to run a few days longer than average.
How the calculator works
The tool adds 340 days to the breeding (cover) date to estimate the expected foaling date. It also shows the foaling window (320 to 370 days) so you know when to start preparing the foaling stall and when to involve your veterinarian if no foal has arrived.
Equine pregnancy timeline at a glance
- Day 14–18: first ultrasound, twin check.
- Day 28: heartbeat confirmation.
- Day 45: endometrial cups form, pregnancy stabilises.
- Day 60: optional fetal sex determination by ultrasound.
- Months 5, 7, 9: EHV-1 (rhinopneumonitis) vaccinations to prevent abortion.
- Month 10: rotavirus and pre-foaling boosters to enrich colostrum.
- Day 320+: move to foaling stall, watch udder development and waxing.
- Day 340: average foaling date.
See more tools: All free equine tools · Reproduction module · Horse management software