Free ranch tool
Cattle gestation & calving calculator
Every gestation calculator gives you a due date. This one forecasts your whole season: enter bull turnout and pull dates and see expected calves per week, your peak week, and how tight your calf crop should be — then put the key dates on your phone's calendar with one tap.
Why forecast the whole season?
A single due date helps with one cow. The shape of the season is what you actually staff and feed against: when the first calf can realistically hit the ground, which week will be the busiest, and what share of the herd should be done after two cycles. Preg-check data tells you this after the fact — the forecast gives you the planning shape months earlier.
The first-21-days number doubles as a herd report card. If the model says 60% and your barn tally comes in far under it, that gap is a bull, body-condition, or disease question worth asking while it's cheap to answer.
HerdCommand records every calving as it happens — ease, dam, sire line, and how the calf got started — so next year you compare the forecast against your herd's real distribution.
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Common questions
How long is cattle gestation?
Around 283 days on average, but it varies by breed: Angus average about 283 days, Hereford 285, Simmental 286, Charolais 289, and Brahman-influenced cattle can run 292 or more. Individual cows vary ±5–10 days around their breed average, so treat any projected date as the middle of a window, not an appointment.
How does the whole-season forecast work?
Cows cycle roughly every 21 days. The forecast assumes a share of open cows conceive each cycle (60% per cycle is a common planning figure for a healthy herd), spreads those conceptions across each cycle, and shifts everything forward by gestation length. The result is the classic front-loaded calving distribution — most calves in the first two cycles, a tail after that. It is a planning shape, not a promise: actual results depend on bull power, cow condition, and weather.
What percentage of cows should calve in the first 21 days?
Most veterinarians and extension specialists point to 60–65% of exposed cows calving in the first 21 days as the mark of a well-managed herd. A low first-cycle percentage usually traces back to cow body condition at breeding, bull fertility, or disease — and it costs real money, because later calves are lighter at weaning.
When should I preg check?
Ultrasound can confirm pregnancy from roughly 30–35 days after breeding; rectal palpation is typically reliable from 45+ days. Checking early and aging the pregnancies tells you how your calving will be distributed months before it starts — which is exactly what the forecast on this page estimates.
When do I give scours vaccinations?
Dam vaccination timing depends on the product, but common label programs put the dose 6–9 weeks before calving, sometimes with a booster closer to calving for first-calf heifers. Use the calendar download to put the window on your phone, and follow your product label and veterinarian.