Horse Gestation Calculator
Calculate your mare's foaling date from breeding date using the 338-day average horse gestation. Free pregnancy due date calculator with foaling range chart.
About This Calculator
The Horse Gestation Calculator helps horse owners, breeders, and veterinarians determine a mare's expected foaling (due) date from the breeding date. Using the average horse gestation period of 338 days (about 11 months), the calculator provides the expected foaling date along with a safe foaling range of 320 to 370 days and real-time pregnancy progress tracking.
Horse pregnancy (gestation) typically lasts 330-345 days, though normal deliveries can occur between 320 and 370 days after successful breeding. The calculator adds 338 days to the breeding date to compute the expected foaling date, with the full foaling range calculated from day 320 (earliest safe) to day 370 (latest expected). The pregnancy progress is shown in weeks along, days along, days remaining, and current gestation week, with a visual timeline chart covering the full 49-week (11-month) pregnancy.
Understanding horse gestation is critical for proper broodmare management. Key signs of approaching foaling include udder development (2-4 weeks before), waxing of the teats (24-48 hours before), relaxation of the tailhead and vulva, and restlessness or isolation behavior. Mares typically foal at night, and the actual foaling process (stage 2 labor) usually takes 15-30 minutes. The first milk (colostrum) is essential for the foal's immune system and must be ingested within the first 12-24 hours of life.
The formula used by the calculator is: Expected Foaling Date = Breeding Date + 338 days. The foaling range is calculated as Breeding Date + 320 days (earliest) to Breeding Date + 370 days (latest). Current days along is calculated as Today's Date - Breeding Date. The gestation week is derived from dividing days along by 7, capped at the total gestation weeks (49 weeks for 338 days).
Regional Notes
All Regions: Horse gestation is a biological constant that does not vary by country. The 338-day average applies worldwide for standard horse breeds. Ponies and miniature horses may have slightly shorter gestations (as low as 320 days) while draft breeds may go longer (up to 370 days). Always consult a veterinarian for individualized broodmare care.
Frequently Asked Questions
How long is a horse pregnant for?
A typical mare is pregnant for 330-345 days, with the average horse gestation period being 338 days (about 11 months). Larger horses tend to have slightly longer pregnancies than ponies.
How do I calculate my mare's foaling date?
Enter the breeding (mating) date into the calculator. The expected foaling date is calculated by adding 338 days to the breeding date. The foaling range is 320 to 370 days after breeding.
What is the foaling range for a horse?
The full foaling range is 320 to 370 days after breeding. Most mares foal between 330 and 345 days. The earliest safe foaling date is day 320, and the latest is day 370.
How can I tell how far along my mare is?
Count the number of days from the breeding date to today. That is your mare's current pregnancy day. Divide by 7 to get weeks along. The calculator does this automatically when you enter the breeding date.
When is breeding season for horses?
Breeding season for horses lasts through spring and summer, typically from May to August. These months have the highest chances of successful conception for mares.
Can I share my horse gestation calculation results?
Yes, the URL saves your inputs so you can bookmark or share the exact calculation with your veterinarian or breeder.
Do all horse breeds have the same gestation length?
No, larger horse breeds tend to have slightly longer pregnancies than ponies or miniature horses. The 338-day average is for standard-sized horses. Ponies may foal earlier while draft breeds may go slightly longer.