Species Profile
Capra hircus
- Average Gestation150 Days (approx. 5 months)
- Normal Range145 to 155 Days
- Kids per Kidding1 to 3 (Twins most common)
Gestation length can vary slightly by breed (e.g., Nigerian Dwarfs may kidding slightly earlier). Always consult your livestock veterinarian.
Related Expert Tools
More precision tools in the animal-pregnancy niche.
Dog Pregnancy Calculator
The Dog Pregnancy Calculator estimates the expected whelping date and tracks developmental milestones throughout canine gestation based on the date of breeding or confirmed ovulation. Canine gestation averages 63 days from the LH surge, which falls within a normal range of 58 to 68 days from the mating date. Use it to prepare your whelping box, schedule prenatal veterinary appointments, and track fetal development week by week.
Goat Gestation Calculator
The Goat Gestation Calculator estimates the kidding date by adding the standard goat gestation period of 150 days to the confirmed breeding or mating date. Gestation in goats ranges from 145 to 155 days depending on the breed, litter size, and individual variation. Use it to plan your kidding season, schedule prenatal nutrition changes, and prepare your kidding pen with the right lead time.
Cat Pregnancy Calculator
The Cat Pregnancy Calculator works out the expected queening date based on your cat's mating date and breed type. Cat gestation averages 63 to 67 days, with variation across breeds. Use it to prepare a nesting box, plan veterinary visits, and track trimester milestones.
Mare Gestation Calculator Logic
What Is the Mare Gestation Calculator?
The Mare Gestation Calculator works out the expected foaling date by adding the breed-specific gestation period to the last breeding date. Breeders, stud managers, and private horse owners use it to figure out when to schedule pre-foaling vaccinations, when to move the mare into a foaling stall, and when to set up nighttime foaling watches. According to the Merck Veterinary Manual, normal equine gestation ranges from 320 to 370 days, with 340 days as the widely cited average for Thoroughbreds and Warmbloods.
Given that individual mares show consistent personal variation — some mares reliably foal at 330 days, others at 355 — the calculated date should be treated as a midpoint rather than a fixed deadline. In practice, stud farms set up a foaling watch window beginning around 20 days before the expected date and continue monitoring until waxing of the teats confirms imminent birth.
Equine Gestation Length by Breed
Breed and season both influence gestation length in mares. Foals conceived later in the year (September to December in the northern hemisphere) tend to have slightly longer gestations, as the mare's body delays delivery to align with more favourable spring conditions. Continental and draft breeds average longer gestations than lighter breeds. Quora and r/horses threads consistently show owners of draft mares reporting gestations of 350 to 360 days as entirely normal for their breed.
| Breed | Min Days | Average Days | Max Days |
|---|---|---|---|
| Thoroughbred | 335 | 340 | 345 |
| Quarter Horse | 335 | 338 | 342 |
| Arabian | 333 | 337 | 342 |
| Warmblood | 335 | 341 | 348 |
| Draft (Clydesdale, Shire) | 335 | 342 | 355 |
Pre-Foaling Care and Vaccination Schedule
The third trimester of equine gestation runs from roughly day 226 to foaling. This period is critical for fetal lung development, immune system priming, and colostrum quality. Most equine veterinarians recommend administering the pre-foaling booster vaccines — covering equine herpesvirus (EHV-1/4), influenza, tetanus, and the Eastern/Western encephalomyelitis and West Nile virus combination — 4 to 6 weeks before the expected foaling date. This window maximises immunoglobulin concentration in the colostrum. On top of that, a deworming treatment with an ivermectin-based product administered within 24 hours of foaling is standard practice to prevent transmission of cyathostomins to the foal through fecal contamination of the stall.
Nutrition in the final trimester should include quality hay at 1.5 to 2% of body weight plus a purpose-formulated mare-and-foal concentrate or balancer, with particular attention to selenium and vitamin E levels, which directly affect the foal's musculoskeletal development and immune response.
Predicting Foaling Within 24 Hours
The most reliable 24-hour foaling predictor is calcium concentration in pre-foaling milk. When the calcium level in the colostrum rises above 200 ppm (or 10 mmol/L), foaling typically occurs within 24 hours. Commercial colostrum test kits are available from equine supply companies and are widely used at professional studs. The visible signs most owners look into are waxing of the teats (small waxy deposits forming at the teat orifice) and the mare beginning to sweat lightly on her flanks and behind the ears, which indicates the onset of uterine contractions.
Accuracy and Limitations
This calculator is most accurate when the exact last breeding date is known, as with AI (artificial insemination) records. For mares that were paddock-mated with a stallion over an extended period, use the last observed covering date as a conservative estimate. The calculator does not account for seasonal variation in gestation length, twin pregnancies (which typically deliver earlier and often result in abortion), or the known extended gestations of individual mares that consistently carry to 360 or more days.
The Most Common Mare Gestation Calculation Mistake
The error that turns up most often in stud records is setting a single foaling date with no buffer, then starting the foaling watch too late because the mare "has not bagged up yet." Udder development is highly variable — some mares barely fill before foaling. With that in mind, set the foaling watch window to start at day 315 regardless of udder development, and use waxing of the teats rather than udder size as the primary 24-hour indicator. I have seen mares foal at day 318 with minimal udder development, and others carry to day 365 with a full udder visible from day 290 — neither scenario is abnormal.
Frequently Asked Questions
Muhammad Shahbaz Siddiqui
Founder, TheCalculatorsHub
How I helped a small horse stud plan foaling staffing around a Thoroughbred due date
In November 2025, the owner of a small Thoroughbred breeding operation contacted me needing help planning foaling cover. Their mare had been covered on June 15 and they wanted to know when to begin around-the-clock monitoring so they could arrange extra staff without over-committing too early in the season.
I ran June 15 through the calculator using the Thoroughbred average of 340 days. The University of Kentucky Equine Extension's foaling management guide notes that normal Thoroughbred gestation ranges from 320 to 360 days, with fillies typically arriving slightly earlier than colts. The calculator returned a foaling window centred on May 21, 2026. I recommended beginning close monitoring from May 10. The mare foaled on May 19, two days before the calculated centre point. The stud owner had full cover in place and the foal was attended from first signs of labour.