Quick answer
Bovine due date = breeding date + the species’ gestation length. That is about 283 days for cattle, 279 for bison, 262 for yak and 310 to 330 for water buffalo.
A river buffalo bred on April 1 is due around Feb 5. A cow bred the same day would calve around Jan 9.
Using the bovine gestation calculator
Open the breed list and scroll to the bottom. The last group, Other bovine species, has bison, yak and both types of water buffalo. Everything above that is cattle, sorted into British, Continental, tropical and dairy breeds.
Then enter what you know. If you have a breeding or AI date, use that. If a vet has aged the pregnancy at a scan, switch to Calving date and type the days pregnant instead. The bovine gestation calculator works backwards to the likely breeding day and forwards to the due date.
Gestation length used for each species
| Bovine species / type | Average gestation | Usual range (days) | Months | Bred Apr 1 → due |
|---|---|---|---|---|
| Domestic cattle, European typeBos taurus | 283 days | 279–287 | 9.3 | Jan 9 |
| Dairy cattle (Holstein, Jersey)Bos taurus | 279 days | 274–284 | 9.2 | Jan 5 |
| Zebu cattle (Brahman)Bos indicus | 292 days | 285–298 | 9.6 | Jan 18 |
| American bisonBison bison | 279 days | 270–293 | 9.2 | Jan 5 |
| YakBos grunniens | 262 days | 257–270 | 8.6 | Dec 19 |
| Water buffalo, river type (Murrah)Bubalus bubalis | 310 days | 305–315 | 10.2 | Feb 5 |
| Water buffalo, swamp typeBubalus bubalis | 330 days | 320–340 | 10.8 | Feb 25 |
These are averages from breed records and published studies. Buffalo and bison figures vary more than cattle figures do, partly because fewer large datasets exist. If your own herd records show a different average, type it under More options → my own gestation and the calculator will use your number.
Water buffalo: river vs. swamp
This is where a generic cow calculator goes most wrong. A river buffalo, the dairy type kept across South Asia, Italy and Egypt, averages around 310 days. A swamp buffalo, the draught type common in Southeast Asia, is closer to 330. Using 283 days for either would put the due date a month too early.
Buffalo heats are also quieter than cattle heats, so breeding dates are often less certain. A pregnancy scan with a fetal age estimate is worth having.
Bison and yak
Bison calve in a fairly tight spring window. Gestation usually falls between 270 and 293 days, with most calves around day 275 to 280. The calculator uses 279. Yak are shorter, at roughly 257 to 270 days. If you run yak or yak crosses, check the date against your own calving records after the first season.
For vets and students: fetal age to due date
Vets often know the fetal age before they know the breeding date. A heifer scanned at 65 days, for example. Choose Calving date, type 65 into days pregnant, and pick the species. For early scans, crown-rump length is the most accurate way to age the fetus. Before day 55 it predicts calving to within about four or five days. The bovine gestation chart lists the main fetal milestones by day.
Bovine gestation calculator FAQ
How do I calculate bovine gestation?
Add the species’ average gestation length to the breeding date: about 283 days for cattle, 279 for bison, 262 for yak, and 310 or 330 for river or swamp buffalo.
Does this work for water buffalo?
Yes. Choose River buffalo or Swamp buffalo under Other bovine species. The difference between them is about three weeks.
Can I use a fetal age from an ultrasound?
Yes. Pick Calving date and enter the days pregnant. The calculator gives the breeding date and due date for the species you selected.
Why is my buffalo’s due date so much later than a cow’s?
Because buffalo pregnancies are about four to seven weeks longer than cattle pregnancies.
Last updated October 21, 2026 · Every date on this page comes from the same data the calculators use.