Add a standard gestation length (default 283 days) to a breeding or AI date to plan calving — or work backward from a target calving date.
Use this when you logged a breeding, AI, or bull-turnout exposure date and need a planning due date and prep window for labor, nutrition, and calving facilities.
Average cattle gestation is about 283 days; many herds use 279–292 as a normal range. Breed, calf sex, and twins can shift the actual date.
Forward mode adds gestation days to the breeding date. Reverse mode subtracts gestation days from the target calving date.
calving = breeding_date + gestation_days
breeding = calving_date − gestation_days
window = result ± window_days
Default 283 days matches common beef/dairy planning tables; adjust if your breed guide differs.
Bred 15 Mar 2026 at 283 days → due about 23 Dec 2026. With a ±7 day window, watch roughly 16–30 Dec 2026.
Assumptions: single calendar-day arithmetic; gestation length is a planning average.
Limits: not ultrasound confirmation, not veterinary advice. Exposure to a bull for weeks produces a range of possible conception dates.
Responsibility: confirm pregnancy with your veterinarian; prepare facilities before the early edge of the window.
It is the widely used average for cattle. Some dairy breeds calve a few days earlier; some beef/Bos indicus lines run longer.
For AI, use the service date. For natural service, use first exposure or the midpoint of turnout if heats were not recorded — expect a wider window.
Same gestation math; heifers may need closer observation near term.