Animal Gestation Calculator & Due Date Charts
Enter a breeding date and get the due date, the normal range and every milestone in between.
This free animal gestation calculator turns a breeding, mating or ovulation date into an expected birth date, together with the earliest and latest dates that are still normal for the species. It covers 75 livestock, pet, rodent, bird, fish and wild species (see every calculator), adjusts for breed where breed data exists, and lays out the checks, feed changes and preparation dates you should plan between conception and birth.
Cow due date
Bull calves are typically carried slightly longer than heifer calves.
Estimated calving date
Friday, 6 August 2027
Earliest
2 Aug 2027
Latest
15 Aug 2027
0 of 283 days elapsed
Milestone timeline
| Day | Milestone | Date |
|---|---|---|
| 30 | Pregnancy check by ultrasound | 26 Nov 2026 |
| 223 | Dry off (60 days pre-calving) | 7 Jun 2027 |
| 253 | Pre-calving vaccinations | 7 Jul 2027 |
| 273 | Move to calving pen | 27 Jul 2027 |
| 283 | Expected calving | 6 Aug 2027 |
Average gestation periods at a glance
Larger animals generally carry their young longer, but development at birth matters just as much. Foals and calves stand within hours and need long gestations, while puppies, kittens and kits are born blind and helpless after only a few weeks.
Gestation calculators by animal
Livestock planning revolves around herd calendars: drying off, vaccination, feed budgets and staffing at birth. Pet planning is shorter and tighter, so a few days of error matters more, and whelping or queening preparation starts within weeks of mating.
Livestock
Cow
283 days average gestation
Horse
340 days average gestation
Sheep
147 days average gestation
Goat
150 days average gestation
Pig
114 days average gestation
Donkey
365 days average gestation
Alpaca
345 days average gestation
Llama
350 days average gestation
Camel
395 days average gestation
Water buffalo
310 days average gestation
Rodents and small pets
Wild animals
Egg layers
Animal gestation chart: all species compared
| Species | Average days | Months | Range | Litter size |
|---|---|---|---|---|
| Cow gestation period | 283 | 9.3 months | 279–292 | 1 calf |
| Horse gestation period | 340 | 11.2 months | 320–370 | 1 foal |
| Dog gestation period | 63 | 2.1 months | 58–68 | 1-12 puppies |
| Cat gestation period | 64 | 2.1 months | 61–67 | 3-5 kittens |
| Rabbit gestation period | 31 | 1.0 months | 28–33 | 4-12 kits |
| Sheep gestation period | 147 | 4.8 months | 144–152 | 1-2 lambs |
| Goat gestation period | 150 | 4.9 months | 145–155 | 1-3 kids |
| Pig gestation period | 114 | 3.7 months | 112–116 | 8-12 piglets |
| Donkey gestation period | 365 | 12.0 months | 340–390 | 1 foal |
| Alpaca gestation period | 345 | 11.3 months | 335–355 | 1 cria |
Read the range column as the window in which a healthy birth normally happens, not as an error bar on the average. Published figures differ between sources because studies use different breeds, herd sizes, climates and starting points, some counting from mating and others from ovulation or embryo transfer, so averages shift by several days.
Full animal gestation comparison chart · Animal breeding calendar by species
How the gestation calculator works
Step 1
Pick the species, and the breed where one is listed.
Step 2
Enter the breeding date, or a target due date to work backwards.
Step 3
Read the due date, the range and the milestone timeline, then print or copy them.
All results are estimates based on published breed averages, not a guarantee of the actual birth date. Breed, the age and parity of the mother, litter size and whether you count from mating or from ovulation each shift the outcome by days, so treat the date as the middle of a window and prepare early.
Why gestation length varies
Breed is the largest single source of variation within a species. Holstein and Jersey cows average about 279 days while Brahman cows average 292, nearly two weeks apart on the same species page. Dog breeds vary less in days but far more in proportion, because a 63-day pregnancy leaves little room for error. Gestation length is moderately heritable and is influenced by the genetics of the young as well as the mother, which is why the sire's breed can move a calving date.
The date you count from matters as much as the number you add. A mating date is an imprecise anchor: sperm survive for days in the reproductive tract, the egg matures a couple of days after ovulation, and many females accept mating either side of their fertile window. Counting from an ovulation date confirmed by progesterone testing narrows a canine due date from a week of uncertainty to roughly two days, and the same logic applies wherever ovulation can be timed.
Litter size pulls in the opposite direction. Multiple young usually shorten gestation, because the uterus reaches its capacity sooner and labour is triggered earlier: twin calves typically arrive five to ten days early, and large litters of puppies or kits often come a day or two before a singleton would. Maternal age, body condition, nutrition, heat stress and season each add a further day or two, which is why any calculated date is a planning midpoint rather than an appointment.