Cow Gestation Calculator

Enter the breeding or AI date. You get the calving date, the normal calving window and a cattle pregnancy calendar you can save.

Pregnancy calendar and key dates

Check with your vet. This is an estimate from average gestation lengths. Your vet can confirm the pregnancy, date it more closely, and tell you when to call for help at birth.

How long is a cow pregnant?

A cow is pregnant for about 283 days, a little over nine months. University of Nebraska beef specialists give a normal range of 279 to 287 days. Breed matters, and cows carrying bull calves tend to go a little longer than cows carrying heifer calves.

The 283 day figure is the one extension services use in their calving tables. The NDSU Calving Book prints its whole table on 283 days. The UNL Beef FAQ gives the 279 to 287 day range. The Merck Veterinary Manual lists cattle at 9 months.

How to use the calving calculator

Pick the date the cow was bred by AI, or the day the bull went in with her. The tool adds 283 days for the calving date. It also shows the 279 to 287 day window and dates for pregnancy checks and dry off.

1. Choose Cow in the animal box (it is already set on this page).
2. Enter the breeding date. For pasture breeding, use the first day the bull was with the herd. That gives the earliest likely calving date.
3. Read the due date and the window. Then save the dates to your phone with Add to calendar.

For a whole herd, run the first and last day of the breeding season. The two due dates show when your calving season starts and ends.

Cattle due date formula

Calving date equals breeding date plus 283 days. The window runs from breeding date plus 279 days to breeding date plus 287 days. The tool counts real calendar days, so leap years are handled for you.

Calving date = breeding date + 283 days

Worked example: a cow bred on January 1, 2025 is due on October 11, 2025. That matches the first line of the NDSU table. NDSU notes that its printed table is one day off in some leap years. A date calculator does not have that problem.

Key dates in a cow pregnancy

Ultrasound or a blood test can confirm pregnancy from about 28 days after breeding. Rectal palpation usually needs about 40 days or more. Dairy cows are often dried off about 60 days before calving, though Penn State reports shorter dry periods can work.

• Day 28 and later: ultrasound and blood tests can find a pregnancy, per NDSU. Only ultrasound can show the calf's heartbeat and sex.
• Day 40 and later: palpation by a trained person.
• Dairy dry off: the calendar marks 60 days before the due date. Penn State Extension notes first lactation cows did best with 40 to 50 dry days and older cows with 30 to 40 in one study, and that no dry period cuts the next lactation's milk by 20% to 25%.

Questions people ask

Other animals

• Horse: 340 days
• Dog: 63 days
• Goat: 150 days
• Sheep: 147 days
• Pig: 114 days
• Cat: 65 days
• Rabbit: 31 days
• Alpaca: 342 days

References

1. FAQ: Pregnant cows, timing of pregnancy. University of Nebraska Lincoln, UNL Beef.
2. Calving Book (AS1954), gestation table based on 283 days. North Dakota State University Extension, revised March 2025.
3. Options for Pregnancy Diagnosis in Beef Cattle. NDSU Agriculture (S. Zoca, University of Tennessee).
4. How Long Should the Dry Period Be?. Penn State Extension, updated April 2025.
5. Approximate Gestation Periods (table). Merck Veterinary Manual.

Written and checked by the Gestation Calculator team against the sources above. Last updated October 20, 2026. How we build these numbers.