Cow Gestation Period

How long is the cow gestation period?

The cow gestation period is the time from the day she is bred to the day she calves. For cattle the textbook number is 283 days. You will find it on breed association charts, on most printed gestation tables and in nearly every vet school lecture, and it is still a perfectly good number to plan around.

Real herds wobble around it. A normal, healthy cow can calve on any day from about 273 to 293, so treat 283 as the middle of a three-week window and not as an appointment. Large studies of beef herds bred by AI now put the average a little shorter, nearer 279–281 days. Breeders have spent decades choosing bulls that sire small, easy-born calves, and those bulls tend to sire shorter pregnancies as well.

Count day 0 as the day of breeding (the AI date, or the day the bull covered her). Add the gestation length to that date and you have her due date. The tool above does the counting for you and shows what the number looks like in weeks and months.

Cow gestation period in days, weeks and months

People ask the question three ways, so here are all three answers for an average cow:

Months are the slippery unit. A calendar month is 28 to 31 days long, so “9 months and 10 days” is exact only for some breeding dates. A cow bred on January 1 is due on October 11, which is 9 months and 10 days. A cow bred on May 1 is due on Feb 8, which is 9 months and 7 days, because the months in between are longer. When a vet tells you she is “five months along”, they usually mean about 150 days.

Cow gestation period by breed

Breed is the biggest single reason one cow calves earlier than another. The difference from the shortest to the longest common breed is about two weeks:

Months + days are counted on the calendar from a January 1 breeding; from other dates they can differ by a day or two.

A few patterns stand out. Dairy breeds such as Holstein, Jersey and Ayrshire carry for about 279 days, while Brown Swiss is the long exception at about 290. British beef breeds sit close to the 283-day rule: Angus a little under it at about 280, Hereford a little over at about 285. Continental breeds such as Simmental, Charolais and Limousin run 286–289 days. Bos indicus cattle such as Brahman are the longest, at about 292 days.

There are pages for the breeds people search for most: the Angus gestation calculator, the Hereford gestation chart and the dairy cow gestation calculator for Holstein, Jersey and Brown Swiss. All 21 breeds are side by side on the cattle gestation calculator.

What makes a pregnancy shorter or longer

Once you know her breed, these are the other things that move the date. Each one is small on its own, but they add up:

• The bull. Gestation length is strongly inherited, so the sire of the calf matters as much as the cow. Some breed associations publish a gestation length EPD for each bull, and a bull at −5 days will move every calf he sires by about that much.
• Calf sex. Bull calves are carried about a day longer than heifer calves. If you used sexed semen or had a fetal-sexing scan, set the calf’s sex under More options.
• Twins. Twins usually come one to two weeks early, and the cow often needs help. A cow that is unusually big for her stage is worth a scan.
• Her age. First-calf heifers carry about as long as cows, perhaps a day less. Very old cows can run a little longer.
• Her health. Heat stress, a sudden illness or very poor feed can bring a calf early. A calf more than about three weeks early is premature and often weak.

What does not matter much is the time of year or how many calves she has had before. Those effects are a day or less in most studies.

Is a heifer’s gestation period different?

No, not by much. A heifer that is bred at 14–15 months carries her first calf for about the same length of time as a mature cow of her breed, sometimes a day shorter. The difference with heifers is everything around the pregnancy. They are still growing, so they need better feed. They have more trouble calving, so they need watching. And they take longer to come back into heat afterwards, so they need more time before the next breeding season. That is why most herds breed heifers two to four weeks before the cows.

The cow gestation period by trimester

Split 283 days into three and each trimester is about 94 days. They are a handy way to think about feeding and care:

1. First trimester (days 0–94). The embryo attaches, the organs form and the heartbeat appears. Pregnancy can be confirmed from about day 28–35. Keep her calm and on a steady diet; this is when most early losses happen.
2. Second trimester (days 95–189). The calf grows from rat-size to small-dog size. Her own needs are lowest now, so this is the cheapest time to put weight back on a thin cow.
3. Third trimester (days 190–283). Most of the birth weight goes on in these last three months. She needs more energy and protein, and you need to plan vaccines, the calving area and, on a dairy, the dry-off date.

For a month-by-month version with what to do and when, see the cow gestation chart. For fetal size by day, see the bovine gestation chart.

How far along is my cow?

If you know the breeding date, put it into the tool above. It shows how many days, weeks and calendar months pregnant she is today, which trimester she is in and how many days are left. If you only know a range, such as a bull that was in for two months, use the date the bull went in for the earliest possible calving and the date he came out for the latest.

If you only know what the vet found at a pregnancy check, work backwards. Say the vet calls her 100 days pregnant on the day of the check. She was bred about 100 days before that, and she is due about 183 days after it, a little over six months. The cow due date calculator takes a vet’s days-pregnant figure directly and gives the date.

And if you know the due date but not the breeding date, count back. A cow due on April 1 was bred around Jun 22. Today’s count of days pregnant is just today minus that date.

Cow gestation compared with other animals

A cow carries her calf for about as long as a woman carries a baby. Here is where she sits among other farm animals:

For comparison, a human pregnancy is about 266 days from conception, or the familiar 280 days counted from the last period. Buffalo, bison and yak have their own page under bovine gestation.

How soon can a cow be pregnant again?

A cow usually comes back into heat 40 to 60 days after calving, later if she is thin or a first-calf heifer. Most herds start breeding again around day 50. To have a calf every 12 months, a 365-day calving interval, she has to be pregnant again by about day 82 after calving, because 365 − 283 = 82. Miss that and she calves later every year until she drops out of the calving season. The cattle breeding calendar works out those dates for the whole herd.

Cow gestation period FAQ

Last updated November 9, 2026 · Every date on this page comes from the same data the calculators use.