Cow Gestation Calculator

How to use the Cow Gestation Calculator#

1. Enter the breeding date. Use the date of mating, or of insemination.
2. Check the length. Leave the average, or enter your vet’s figure for the breed.
3. Read your dates. You get the expected date, the likely window and your cow’s progress.

How long is a cow pregnant?#

The average is about 283 days, with most calves arriving between 279 and 290 days. Beef breeds can run a little longer than dairy breeds, and bull calves are often carried a day or two longer than heifer calves.

Getting ready for the calf#

Dairy cows are usually dried off about 60 days before calving, which gives the udder a rest and lets her put more into the calf. In the last weeks, move her to a clean, dry calving area and check her often. Colostrum within the first hours is critical for the calf.

Pregnancy can be confirmed by a vet by palpation or ultrasound from about a month after service. Call the vet if labour doesn’t progress or if you can see a problem with the calf’s position.

Why the date is a window#

Most calves arrive between day 279 and 290, a window of about eleven days. Breed makes a difference: beef breeds tend to run longer than dairy breeds, and a bull calf is often carried a day or two longer than a heifer calf. Once you have a few seasons of records, your own herd’s average is a better guide than this one. This calculator is a planning tool and doesn’t replace veterinary advice.

A worked example#

A cow is bred by artificial insemination on Sat 20 February 2027. Using the 283-day average, the due date is Tue 30 November 2027. The likely window starts on Fri 26 November 2027 (day 279) and ends on Tue 7 December 2027 (day 290). Halfway is Mon 12 July 2027, and the final stretch begins on Tue 19 October 2027, day 241.

If the herd is on a seasonal calving pattern, this is the date that decides whether the calf arrives onto good spring grass or into a muddy shed, so it is worth working out before the bull or the straw goes in.

Breed, sex and number change the length#

The 283-day figure is an average across beef and dairy cattle, and breeds sit either side of it. Holstein cows tend to run a little shorter, around 279 days, while many beef breeds and Bos indicus types such as Brahman run longer, sometimes 290 days or more. Bull calves are usually carried a day or two longer than heifer calves, and twins arrive earlier, often by a week or so.

If your breed society or vet quotes a different average, type it into the length box. The window then moves with it. For a herd record, it helps to note the actual calving dates for a few seasons, because your own herd’s average is a better guide than any textbook figure.

Planning around the due date#

Dairy herds normally dry off a cow about 60 days before she is due, which in this example is Fri 1 October 2027. Many farms also move heavily pregnant cows to a clean calving pen a week or two ahead, and use the final-stretch date as the cue to start checking more often.

Look for a full udder, loosening of the ligaments either side of the tailhead, a swollen vulva and clear mucus. Calving usually goes without help, but a cow that strains hard for an hour without visible progress needs her vet. Calves should get colostrum quickly, and a rough target is about a tenth of the calf’s body weight over the first day.

Pregnancy itself can be confirmed earlier than most people expect: ultrasound from about four weeks after service, and a vet’s palpation from around five to six weeks.

Keeping the herd record useful#

Write the service date, the sire and the actual calving date for every cow. After two or three seasons you will know whether your cows average closer to 280 or 286 days, and you can type that figure into the length box. Notes on assisted calvings and calf weights help too, since a pattern of difficult births with one bull is something worth spotting before the next breeding season, not after it.

Last reviewed October 2026 by the Calclulo team.