Horse Pregnancy Calculator
Plan for your mare's pregnancy with precision
Calculate when your mare is due to give birth with this equine pregnancy calculator. Enter the date of the first breeding below and you will be given expected pregnancy dates so you can prepare for foaling.
Expected Due Dates:
The estimated due date is 340 days from the first breeding, which is the length of gestation in equines. The expected dates indicate the earliest and latest expected dates of delivery. Dates may vary in some instances.
Your Mare's Pregnancy Timeline:
Horse Pregnancy Calculator
Estimate your mare’s foaling date with ease by entering the breeding or ovulation date.
Horses typically have a gestation period of around 340 days (about 11 months). This tool helps horse breeders and caretakers plan care, monitor fetal milestones, and prepare for foaling.
Important: Always consult an equine veterinarian to confirm pregnancy and monitor foal development for the most accurate planning and health management.
How to Use the Horse Pregnancy Calculator
Using this tool is simple and effective. You’ll need just one key piece of information: the date of successful mating or ovulation.
Steps to follow:
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Select the breeding or ovulation date:
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Choose the date your mare was successfully bred or inseminated.
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If she was covered more than once, use the earliest date.
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Click “Calculate Due Date”:
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The calculator will estimate your mare’s expected foaling window—typically around 340 days later.
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View the pregnancy timeline:
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See key gestation phases, developmental milestones, and signs to expect as the due date approaches.
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Tip: For accuracy, combine this estimate with ultrasound checks and veterinary exams throughout gestation.
What Is the Average Horse Gestation Period?
The average horse gestation period is 338–345 days, though it may vary slightly depending on breed, mare age, season, and overall health.
| Mare Type | Average Gestation Length |
|---|---|
| Light horse breeds | 336–342 days |
| Draft or large breeds | 340–345 days |
| Ponies | 320–330 days |
Note: Colts (male foals) are often carried slightly longer than fillies (female foals), and winter pregnancies tend to last longer than those in warmer seasons.
Horse Pregnancy Timeline: What Happens When?
Horse pregnancies progress through predictable stages. Below is a breakdown of major events and fetal development:
| Stage | Timeframe (Days) | Description |
|---|---|---|
| Fertilization | Day 1 | Ovum is fertilized in the fallopian tubes. |
| Implantation | Days 14–17 | Embryo attaches to the uterine wall. |
| Organogenesis | Days 25–45 | Major organs and heartbeat begin developing. |
| Fetal Growth Phase 1 | Days 50–150 | Skeleton forms; limb buds grow; gender visible via ultrasound. |
| Fetal Growth Phase 2 | Days 150–270 | Significant size and weight gain. |
| Final Development | Days 270–340 | Foal finishes developing lungs, immune system; mare begins udder changes. |
Vet Insight: Most vets recommend an ultrasound at day 14–18 to confirm implantation and detect twins (which may require intervention).
Do Breeds Affect Pregnancy Length in Horses?
Yes, breed and body size can influence gestation length.
| Breed | Gestation Range |
|---|---|
| Thoroughbred | 336–342 days |
| Quarter Horse | 337–343 days |
| Arabian | 334–340 days |
| Draft Horse | 340–345 days |
| Miniature Horse | 320–340 days |
Key Point: Long gestations aren’t always abnormal. A mare going beyond 360 days may still foal normally, but veterinary monitoring is advised.
Signs of Pregnancy in Mares
Detecting pregnancy in horses isn’t always obvious without vet assistance, especially early on. However, mares show both physical and behavioral signs across the trimesters.
Physical Signs:
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No return to heat 16–20 days after breeding
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Slight weight gain from mid-gestation
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Enlarged abdomen (especially after 150 days)
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Udder development begins near day 300
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Softening of pelvic ligaments closer to foaling
Behavioral Signs:
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Reduced interest in stallions
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Mild mood shifts or clinginess
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Less physical activity or changes in appetite
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Nesting behavior close to foaling (pawing, pacing)
Preparing for Foaling at Home
A safe, calm environment helps support a stress-free foaling process for your mare and a healthy start for the foal.
1. Set up a foaling area:
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Clean, well-bedded stall (minimum 14×14 ft)
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Quiet, dimly lit, and free from distractions
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Disinfected foaling kit ready (gloves, towels, iodine, etc.)
2. Observe her closely in the final weeks:
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Daily udder checks for swelling and waxy discharge
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Monitor tail head and vulva for relaxation and softening
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Check body temperature daily for signs of imminent labor
3. Prepare foaling essentials:
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Tail wrap, iodine solution (for umbilical cord)
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Clean bucket, thermometer, flashlight
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Emergency vet contact on standby
4. After birth:
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Ensure foal stands and nurses within 2 hours
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Check mare passes placenta within 3 hours
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Monitor both for complications (retained placenta, poor nursing)
Veterinary Care Timeline During Horse Pregnancy
Regular vet checks are key to detecting issues early and ensuring a safe delivery.
| Stage | Purpose |
|---|---|
| Day 14–18 | Ultrasound to confirm pregnancy and check for twins |
| Day 45–60 | Fetal heartbeat and health scan |
| Day 150–200 | Mid-gestation wellness exam |
| Day 300+ | Pre-foaling check and vaccination |
| Post-birth | Check foal’s vitals and mare’s recovery |
Red Flags:
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Sudden weight loss
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Early udder development before day 300
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Vaginal discharge or colic signs
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Labor lasting more than 1 hour without delivery
Explore More Animal Pregnancy Calculators
Caring for a variety of animals? Our specialized calculators are tailored to species-specific timelines, signs, and care tips:
FAQs – Horse Pregnancy
Can mares show false pregnancy?
Yes, hormonal imbalances or uterine issues can mimic pregnancy. A vet can diagnose this through ultrasound.
Can I ride a pregnant mare?
Light riding is often safe during the first two trimesters but should stop around day 250. Always consult your vet first.
What should I feed a pregnant mare?
Offer a balanced diet rich in fiber, with added protein and minerals (calcium, phosphorus). Consider mare-and-foal formulated feed during the third trimester.
What is “waxing up” in horses?
It’s the appearance of waxy secretions on the teats, usually 24–48 hours before foaling.
How many foals can a mare have?
Usually one foal per pregnancy. Twins are rare and risky—often require veterinary management.
