How long are cows pregnant?
About 283 days [4][6]. Most cows calve 279–287 days after breeding[4][5]; Alabama Extension gives the wider normal range of 273–290 days [6], which is what the calculator shows as earliest and latest.
| Source | What it says |
|---|---|
| University of Nebraska [4] | 279–287 days; 283 common for most breeds |
| Penn State Extension [5] | Typically 279–287 days |
| Alabama Extension [6] | Average 283 days, range 273–290 |
| Merck Vet Manual (table) [1] | About 9 months |
Breed and the sex of the calf
Gestation length differs by breed and by the sex of the calf: cows carrying bull calves tend to go slightly longer than cows carrying heifers [4]. The published breed averages we found disagreed with each other, so this page doesn’t give a separate figure for Angus, Hereford or other breeds. If your breed association publishes one, compare it with the range shown.
Heifers use the same figures here: the sources above give one gestation length for cows and heifers alike.
Worked examples
- AI date. A cow inseminated on May 10, 2027 is due on February 17, 2028. Most calve between February 13, 2028 and February 21, 2028; the full range is February 7, 2028 to February 24, 2028.
- Breeding season. A bull with the herd from May 1, 2027 to June 30, 2027 (about three heat cycles) gives average calving dates from February 8, 2028 to April 8, 2028. Enter both dates above to see the calendar for the season.
When can you preg-check a cow?
| When | What |
|---|---|
| Day 18–24 | Watch for a return to heat. Cows cycle about every 21 days (18–24); an open cow shows heat again around then. [6][2] |
| Day 25 | Blood pregnancy test possible. Pregnancy-protein tests can detect pregnancy from about day 25. [7][3] |
| Day 28–32 | Ultrasound possible. A vet can see a pregnancy by rectal ultrasound from about day 28–32. [7][3] |
| Day 35–40 | Rectal palpation. Skilled palpators can find a pregnancy from about day 35; about day 40 for most. (per Missouri Extension) [7] |
| Day 60–90 | Fetal sexing by ultrasound. Usually done from about day 60 to day 90. (per Missouri Extension) [7] |
- Heat detection. Cows cycle about every 21 days (18–24) [6][2]. A cow seen in heat around then probably didn’t settle.
- Blood or milk test for pregnancy-associated proteins: accurate from about day 25[7][3].
- Ultrasound by a vet: from about day 28–32 [7][3]. It can also age the pregnancy, and from about day 60 to 90 it can tell bull calves from heifers [7].
- Rectal palpation: skilled palpators can find a pregnancy from about day 35, most from about day 40[7].
Common questions
How many months is a cow pregnant?
About 9 months and 10 days: 283 days is roughly 9.3 months [4][1].
Is this a calving calculator for AI or natural service?
Both. For AI, enter the insemination date. For natural service with a known date, enter that. For a bull run with the herd, enter the day he went in and the day he came out.
Can a cow calve before 273 days?
It happens, but it’s outside the normal range the sources give. A calf born well before the earliest date in the calendar is worth discussing with your vet.
Do dairy cows have a different gestation?
The figures on this page come from beef-cattle sources. For a dairy herd, compare the calculator’s dates with your own herd’s calving records.
These dates are planning estimates from published averages, not veterinary advice. Your vet can confirm and age a pregnancy.
Sources
- Merck Veterinary Manual, table “Approximate Gestation Periods”Gestation by species; dog 62–64 days from ovulation, 58–72 days from breeding
- Merck Veterinary Manual, table “Features of the Reproductive Cycle”Estrous cycle lengths (cattle 18–24, sheep 14–20 days); dog puberty 6–24 months
- J. Statham, “Pregnancy Determination in Cattle,” Merck Veterinary ManualUltrasound from 28–32 days; pregnancy proteins rise 24–28 days
- University of Nebraska–Lincoln, UNL Beef FAQ “Pregnant cows, timing of pregnancy…”Gestation 279–287 days, 283 common; bull calves slightly longer
- Penn State Extension, “Beef Cattle Reproduction and Genetics”Gestation typically 279–287 days
- S. P. Rodning et al., “Estrus Synchronization and Artificial Insemination Programs for Beef Cattle,” ANR-1027, Alabama ExtensionAverage 283 days, range 273–290; 21-day cycle (18–24)
- J. Thomas, S. Poock, E. Smith, “Determination of Pregnancy Status in Beef Herds,” MU Extension G2042Blood test from 25 days; ultrasound about 28–30; palpation from 35–40; fetal sexing 60–90