# Cow gestation: when is my cow due?

Computes a cow’s calving date from the breeding date (283 days), the normal calving window of 279 to 287 days, how many days along she is, and when to watch for heat if she did not settle.

- Page: https://www.acalculator.org/biology/cow-gestation-calculator
- JSON spec: https://www.acalculator.org/biology/cow-gestation-calculator.json
- Version: 7542a66763c6

## Default answer

Example with the default inputs (Breeding date July 21, 2026, Today’s date October 19, 2026) on the example date Monday, October 19, 2026: Your cow is due to calve about April 30, 2027, between April 26, 2027 and May 4, 2027.

## Inputs

| Key | Label | Description |
| --- | --- | --- |
| d | Breeding date | The day the cow or heifer was bred (mated or inseminated). |
| on | Today’s date | The day to count from, to show how far along the cow is. |

## Outputs

| Key | Label | Description |
| --- | --- | --- |
| due | Estimated calving date | The breeding date + 283 days. |
| earliest | Earliest normal calving date | The breeding date + 279 days. |
| latest | Latest normal calving date | The breeding date + 287 days. |
| days | Days along | Whole days from the breeding date to today’s date. |
| left | Days to the estimated calving date | Whole days from today’s date to the estimated calving date; negative once it has passed. |
| stage | Where she is now | The stage on today’s date, in one line. |
| heat | Next heat if she did not settle | The breeding date + 21 days, one estrous cycle later. |

## Method

Calving date = breeding date + 283 days; normal window = breeding date + 279 to 287 days; next heat = breeding date + 21 days.

## Assumptions

- The estimate is the average gestation of about 283 days given by Mississippi State University Extension; the window of 279 to 287 days is from Penn State Extension.
- Days count from the breeding date as day 0. Breed, the calf’s sex and the cow’s age change the length a little.
- A cow that did not settle comes back into heat about one estrous cycle (21 days, typically 18 to 24) after breeding.

## Worked examples

1. d = 2026-10-01, on = 2026-12-01 gives due = 2027-07-11, earliest = 2027-07-07, latest = 2027-07-15, days = 61, left = 222, heat = 2026-10-22, stage = Day 61 of about 283: 222 days to the estimated calving date.. Source: Mississippi State University Extension, Publication 2616, The Estrous Cycle of Cattle (after approximately 283 days of gestation, parturition occurs; the cycle averages 21 days, with a typical range of 18 to 24 days), https://extension.msstate.edu/publications/the-estrous-cycle-cattle (retrieved 2026-10-18); Penn State Extension, Beef Cattle Reproduction and Genetics (typically, gestation ranges between 279 and 287 days), https://extension.psu.edu/animals-and-livestock/beef-cattle/reproduction-and-genetics (retrieved 2026-10-18); 1 October 2026 + 279, 283 and 287 days.
2. d = 2027-06-01, on = 2028-03-08 gives due = 2028-03-10, earliest = 2028-03-06, latest = 2028-03-14, days = 281, left = 2, stage = Day 281: in the calving window (days 279 to 287).. Source: Mississippi State University Extension, Publication 2616, The Estrous Cycle of Cattle (after approximately 283 days of gestation, parturition occurs; the cycle averages 21 days, with a typical range of 18 to 24 days), https://extension.msstate.edu/publications/the-estrous-cycle-cattle (retrieved 2026-10-18); Penn State Extension, Beef Cattle Reproduction and Genetics (typically, gestation ranges between 279 and 287 days), https://extension.psu.edu/animals-and-livestock/beef-cattle/reproduction-and-genetics (retrieved 2026-10-18).
3. d = 2026-03-15, on = 2026-12-31 gives due = 2026-12-23, latest = 2026-12-27, days = 291, left = -8, stage = Day 291: past the latest normal calving date (day 287). Call your vet.. Source: Mississippi State University Extension, Publication 2616, The Estrous Cycle of Cattle (after approximately 283 days of gestation, parturition occurs; the cycle averages 21 days, with a typical range of 18 to 24 days), https://extension.msstate.edu/publications/the-estrous-cycle-cattle (retrieved 2026-10-18); Penn State Extension, Beef Cattle Reproduction and Genetics (typically, gestation ranges between 279 and 287 days), https://extension.psu.edu/animals-and-livestock/beef-cattle/reproduction-and-genetics (retrieved 2026-10-18).

## FAQ

### How long is a cow pregnant?

About 283 days, a little over 9 months. Mississippi State University Extension gives about 283 days from fertilization to calving, and Penn State Extension says gestation typically ranges from 279 to 287 days.

### How is the calving date worked out?

The calculator adds 283 days to the breeding date. The earliest and latest normal dates add 279 and 287 days. A cow bred on 1 October 2026 is due about 11 July 2027.

### What if I used a bull and do not know the breeding date?

Type the day the bull went in for the earliest calving date, then the day he came out for the latest. The cow was bred somewhere between the two, during a heat, and heats come about every 21 days.

### When will she come back into heat if she is not pregnant?

The estrous cycle of cows and heifers averages 21 days, with a typical range of 18 to 24 days. Watch for heat about 21 days after breeding; the calculator shows that date. No heat then is a first sign that she settled.

### Do breed and calf sex change the date?

A little. Penn State Extension notes that gestation length varies with breed, body condition, age and the sex of the calf. Use the window of 279 to 287 days, not only the single estimate.

### What if my cow goes past the latest date?

Call your vet. Past day 287 a cow is beyond the normal window, and she should be checked.

## Sources

- Mississippi State University Extension, Publication 2616, The Estrous Cycle of Cattle (J. A. Parish, J. E. Larson, R. C. Vann): after approximately 283 days of gestation, parturition occurs; the estrous cycle averages 21 days, with a typical range of 18 to 24 days. https://extension.msstate.edu/publications/the-estrous-cycle-cattle (retrieved 2026-10-18)
- Penn State Extension, Beef Cattle Reproduction and Genetics: cattle gestation length can vary based on breed, body condition, age and sex; typically, gestation ranges between 279 and 287 days. https://extension.psu.edu/animals-and-livestock/beef-cattle/reproduction-and-genetics (retrieved 2026-10-18)