Horse (Mare) Gestation Calculator

A mare's pregnancy lasts around 340 days — longer than many owners expect — and knowing your foal's estimated arrival date is critical for planning veterinary care, stall preparation, and monitoring. Enter your mare's last breeding date into the Horse (Mare) Gestation Calculator to get her estimated foaling date. Secondary outputs include days pregnant, days until due date, and the earliest safe and latest expected foaling dates.

Enter the last date your mare was bred or conceived

Results

Estimated Foaling Date

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Days Pregnant (Current)

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Earliest Safe Foaling

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Latest Expected Foaling

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Days Until Due Date

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Results Table

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Frequently Asked Questions

How long is the average horse pregnancy?

The average gestation period for a mare is around 340 days (about 11 months), but it can range from 320 to 360 days depending on the breed, season, and individual mare.

How do I calculate my mare's foaling date?

Add 340 days to the breeding or conception date. This gives you the estimated due date, though mares can safely foal anywhere from 330-350 days after breeding.

What's the earliest safe foaling date?

The earliest safe foaling date is typically around 320-330 days after breeding. Foals born before 320 days are considered premature and may require special veterinary care.

How accurate is the estimated foaling date?

The estimated foaling date is a guideline with a typical window of ±10-15 days. Individual mares may vary based on breed, age, nutrition, season, and previous foaling history.

Can I use this calculator for miniature horses?

Yes, but miniature horses and ponies often have slightly shorter gestation periods (around 320-335 days) compared to full-size horses. Consult your veterinarian for breed-specific guidance.

When should I start preparing for foaling?

Begin serious foaling preparations around 30 days before the due date. This includes setting up the foaling stall, gathering supplies, and scheduling pre-foaling veterinary checks.

Why do some mares foal later than 340 days?

Large breeds, older mares, first-time mothers, and seasonal factors can extend gestation. Mares bred in winter often carry longer than those bred in spring. Up to 360 days can still be normal.

Does the foaling date depend on the foal's gender?

There's no significant difference in gestation length based on the foal's gender. Other factors like breed size, mare's age, and environmental conditions have much greater influence on timing.