How long is a cow pregnant? Gestation length by breed
By the RanchOS Global editorial team · Updated
In short: a cow is pregnant for about 283 days, a little over nine months. Breed moves the average by several days, from about 282 days in Angus to about 293 in Brahman, and bull calves are carried about a day longer than heifers.
The number: about 283 days
The Beef Improvement Federation (BIF) says gestation length "averages about 283 days in cattle, but can range based on breed." That is nine months and about ten days. To get a due date, add 283 days to the breeding date: a cow bred on June 1 is due about March 11 of the next year.
Want the date without counting? The gestation calculator does it from a breeding date or a whole breeding season.
Gestation length by breed
These averages come from the USDA Meat Animal Research Center's Germ Plasm Evaluation project, as reported by Oklahoma State University Extension:
| Breed | Average gestation |
|---|---|
| Holstein | 281 days |
| Angus | 282 days |
| Jersey | 283 days |
| Hereford | 284 days |
| Simmental | 289 days |
| Charolais | 290 days |
| Limousin | 291 days |
| Brahman | 293 days |
Averages differ by a few days from one study to the next. BIF cites breed data of 278.6 days for Angus and 284.3 days for Simmental, and a 2024 Journal of Animal Science study reported by Oklahoma State found an overall average of 280.2 days. Use your own breeding and calving dates when you have them.
What else moves the due date
- Sex of the calf. Bull calves are carried a little longer: 1.2 days in Angus and 1.5 days in Simmental data (BIF), and 280.8 days against 279.6 for heifers in the 2024 study.
- Age of the cow. In Simmental data, mature cows carried calves 1.9 days longer than first-calf heifers (BIF).
- Calving season. In the 2024 study, fall-calving cows averaged 279.1 days and spring-calving cows 281.1.
- The cow herself. Individual gestations in that study ran from 253 to 300 days. As Oklahoma State puts it, some cows do not read the book.
Use it to plan
- Treat the due date as the middle of a window. Have the calving kit and the pasture ready before the first date on the list. See the calving season checklist.
- Count back for breeding. To calve every 365 days, a cow has to settle within about 82 days after calving (365 minus 283).
- Write down real dates. Gestation length is the number of days between the breeding date and the calving date. AI dates, observed breedings and ultrasound fetal aging all give you a breeding date to count from.
See also Replacement heifer breeding weight.
Common questions
How many months is a cow pregnant?
About nine months and ten days. The Beef Improvement Federation puts the average gestation length in cattle at about 283 days, with differences between breeds.
Which cattle breed has the longest gestation?
In the USDA Meat Animal Research Center data reported by Oklahoma State University Extension, Brahman cattle averaged 293 days, the longest of the breeds listed, followed by Limousin (291), Charolais (290) and Simmental (289). Angus averaged 282 days and Hereford 284.
Are bull calves carried longer than heifer calves?
Yes, slightly. The Beef Improvement Federation reports that male calves are carried 1.2 to 1.5 days longer in Angus and Simmental data, and a 2024 Journal of Animal Science study cited by Oklahoma State found 280.8 days for bull calves and 279.6 days for heifers.
How do I calculate a cow due date?
Add 283 days to the breeding date, or the average for her breed. A cow bred on June 1 is due about March 11. Treat that date as the middle of a window: in one 2024 study, individual gestations ran from 253 to 300 days.
Sources
- Beef Improvement Federation Guidelines: Gestation length
- Oklahoma State University Extension, Cow-Calf Corner (January 15, 2024): gestation length by breed, USDA-MARC Germ Plasm Evaluation data (Brian Freking)
- Oklahoma State University Extension, Cow-Calf Corner (February 23, 2026): gestation length research (Mark Z. Johnson)