Web Utility Services

Animal gestation calculator

Pick the animal and the breeding date to see the due date, the earliest and latest likely dates, and a pregnancy calendar with test and scan windows.

If the buck ran with the does for a while, enter the day he came out to get a kidding window.

Due date

Pick a date above

Earliest to latest
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Gestation used
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Pregnancy calendar

DateDayWhat to expect

How long are animals pregnant?

These are the average gestation lengths the calculator uses, counted from the breeding date, and the full range that veterinary and extension sources call normal. Each animal’s page shows which source says what.

Gestation length by species (days)
AnimalAveragePublished rangeBirth is called
Goat150 [5][19][1]147–155 [19][17]kidding
Sheep147 [20][21][7]144–155 [20][21][19]lambing
Cattle283 [22][24]273–290 [22][23][24]calving
Pig114 [26][27][1]113–117 [28][10]farrowing
Horse340 [30][31]310–370 [12][30][31][32]foaling
Rabbit31 [33][34][1]28–35 [33][34][13]kindling
Dog63 [14][15][16]56–72 [14][1][15][16]whelping

How the calculator works

It adds the average gestation length to the breeding date. For example, a goat bred onNovember 1, 2026 is due about March 31, 2027: 150 days, or21 weeks 3 days. The earliest and latest dates come from the shortest and longest normal lengths published for that species.

Why sources give different numbers

Breed, the sex of the young and the size of the litter all shift gestation by a few days[22][21][13]. Sources also round differently: Merck’s summary table lists sheep at 150 days [1], while its own sheep chapter and most extension services give 147[7][20][21]. Rather than pick one, the calculator uses the figure most sources share and shows the full published range.

The breeding date isn’t always the day the pregnancy starts, which is one reason a due date is an estimate. In dogs this matters most, because mating can happen days before ovulation: counted from mating, due dates spread over56–72 days, but from ovulation they fall within a few days of 63[1][3][16].

Common questions

How do I calculate an animal’s due date?

Count forward the species’ gestation length from the breeding date: 150 days for a goat, 147 for a sheep, 283 for a cow, 114 for a pig, 340 for a horse, 31 for a rabbit and 63 for a dog. The calculator does this and handles month lengths and leap years for you.

Which of these animals has the longest pregnancy?

The horse, at about 340 days on average and from 310 to 370 days in the normal range[30][31][12]. The rabbit has the shortest, about 31 days [33][34].

Can I use the calculator for other animals?

Not yet. It covers the seven animals above. For cats, alpacas, donkeys and others, ask your vet or a breed association.

Is this veterinary advice?

No. The dates are planning estimates from published averages. Your vet can confirm a pregnancy and tell you what to watch for with your own animal.

Animal pages

Sources

  1. Merck Veterinary Manual, table “Approximate Gestation Periods”Gestation by species; dog 62–64 days from ovulation, 58–72 days from breeding
  2. Merck Veterinary Manual, table “Features of the Reproductive Cycle”Estrous cycle lengths (cattle 18–24, sheep 14–20 days); dog puberty 6–24 months
  3. A. P. Davidson, “Breeding Management of Bitches,” Merck Veterinary Manual (reviewed 2025)Heat interval 4–13 months (average 7); proestrus and estrus 3 days to 3 weeks (average 9); diestrus, anestrus; whelping 64–66 days after the LH peak
  4. A. P. Davidson, “Pregnancy Determination in Bitches and Queens,” Merck Veterinary Manual (reviewed 2025)Palpation, relaxin test, ultrasound and X-ray timing in dogs
  5. S. G. Balch, “Breeding and Parturition of Goats,” Merck Veterinary ManualGoat gestation averages 150 days; 21-day cycle
  6. J. L. Stewart, “Pregnancy Determination in Goats,” Merck Veterinary Manual (reviewed 2026)Blood test from 25 days; ultrasound from 20 (rectal) or 30 days (belly), counting to 85 days; 19–24-day cycle
  7. S. G. Balch, “Breeding, Parturition, and Common Lamb Diseases of Sheep,” Merck Veterinary ManualSheep gestation averages 147 days; 17-day cycle
  8. C. M. Scully, “Pregnancy Determination in Ewes,” Merck Veterinary Manual (reviewed 2026)Ultrasound accuracy after 31 days; fetal count best at 45–50 days
  9. J. Statham, “Pregnancy Determination in Cattle,” Merck Veterinary ManualUltrasound from 28–32 days; pregnancy proteins rise 24–28 days
  10. R. V. Knox, “Breeding Management of Pigs,” Merck Veterinary Manual (reviewed 2026)Average gestation now 115–116 ± 1 days; 18–24-day return to estrus; ultrasound at 26–30 days
  11. P. L. Sertich, “Pregnancy Determination in Horses,” Merck Veterinary ManualTwin check at 14–18 days; heartbeat at 24–25 days
  12. A. S. Munsterman, “Intensive Care and Emergencies in Neonatal Foals,” Merck Veterinary Manual (reviewed 2025)Normal gestation 310 to more than 370 days; premature before 320 days
  13. J. Mayer, “Management of Rabbits,” MSD Veterinary ManualRabbit gestation about 31–33 days; palpate at 12 days; nest box at 28–29 days
  14. C. Barnes, M. Weir, E. Ward, “Breeding for Pet Owners: Pregnancy in Dogs,” VCA Animal HospitalsDog gestation 57–65 days, average 63; palpation, ultrasound and X-ray timing
  15. H. Meyers, “The Reproductive Cycle in Dogs: From Breeding to Birthing,” American Kennel Club (2025)Gestation counted from ovulation, LH surge and breeding; heat stage lengths; pregnancy milestones
  16. Cornell Richard P. Riney Canine Health Center, “The normal whelping process”63 days from ovulation, 63 ± 7 from first breeding; temperature drop within 24 hours
  17. Penn State Extension, “Goat Reproduction and Genetics”Goat gestation 148–152 days
  18. C. Hill, “Are There Any Buns in the Oven? Methods of Pregnancy Testing in Small Ruminants,” Penn State ExtensionBlood tests at 25–30 days; ultrasound from 20 or 30 days, best near 45, counting to 85; 19–24-day cycle
  19. B. Brady, “Reproductive Management—Dairy Goats and Sheep,” Alabama Cooperative Extension System (2019)Goat gestation 150 days; kidding and lambing 147–155 days; cycles; ultrasound at 32 days; breeding table
  20. Pitassi et al., “Sheep Production: Birth to Weaning,” NMSU Circular 703 (2022)Ewe gestation about 147 days (144–152); check ewes 1–2 weeks before
  21. R. Kott, Montana Farm Flock Sheep Production Handbook, “Reproduction,” Montana State University ExtensionAverage 144–151 days by breed (about 147); individuals 138–159; 17-day cycle
  22. University of Nebraska–Lincoln, UNL Beef FAQ “Pregnant cows, timing of pregnancy…”Gestation 279–287 days, 283 common; bull calves slightly longer
  23. Penn State Extension, “Beef Cattle Reproduction and Genetics”Gestation typically 279–287 days
  24. S. P. Rodning et al., “Estrus Synchronization and Artificial Insemination Programs for Beef Cattle,” ANR-1027, Alabama ExtensionAverage 283 days, range 273–290; 21-day cycle (18–24)
  25. J. Thomas, S. Poock, E. Smith, “Determination of Pregnancy Status in Beef Herds,” MU Extension G2042Blood test from 25 days; ultrasound about 28–30; palpation from 35–40; fetal sexing 60–90
  26. J. C. Rea, “Care of Pigs From Farrowing to Weaning,” MU Extension G2500Sow gestation averages 114 days; breeding-to-farrowing table
  27. J. H. Koziol, “What to Expect When: Your Sow is Expecting,” Purdue University VA-30-W114 days (3 months, 3 weeks, 3 days); pregnancy check about 30 days; late-pregnancy signs
  28. M. White, “Farrowing Process,” NADIS Pig Health BulletinTypically 115 days, 113–117 normal; farrowing area 5–7 days before
  29. BPEX “Action for Productivity” no. 29, “Effective Heat Detection,” via The Pig Site (2013)Returns to heat 18–24 days after service
  30. J. H. Koziol, A. C. Farr, “What to Expect When… (mares),” Purdue University VA-26-WAverage 340 days (315–365); udder fills 2–4 weeks before; waxing 1–4 days before
  31. O. Watson, “Foaling Season: Tips for Delivery,” Penn State Extension (2025)330–370 days, most near 340; premature before 320; move to foaling area a week or more before
  32. S. Madill, E. Malone, C. Ward, “Caring for your mare during breeding and foaling,” University of Minnesota ExtensionUsually 335–342 days, occasionally 315–400+; exams at 14–16 and 24–25 days; foaling site 4–6 weeks before
  33. Oregon State University Extension, “Raising Rabbits for Meat: Providing Basic Care,” EC 1655Gestation 28–35 days, average 31; litter hard to feel in the first 10 days
  34. American Rabbit Breeders Association, FAQsGestation 28–32 days, 31 average; palpate days 10–12; nest box days 25–27; past 35 days abnormal
  35. R. Shaeffer, L. F. Kime, J. K. Harper, “Rabbit Production,” Penn State ExtensionAverage gestation 31–32 days; nest box at 28 days

Last reviewed . Found a mistake? Let us know.