# When is my dog pregnancy due?

Computes the whelping date window of a pregnant dog from the breeding, LH surge, ovulation or diestrus date, with how many days along she is and when ultrasound and X-ray checks work.

- Page: https://www.acalculator.org/days/dog-pregnancy-calculator
- JSON spec: https://www.acalculator.org/days/dog-pregnancy-calculator.json
- Version: 8207ec253220

## Default answer

Example with the default inputs (The date I know First breeding, Date of that event September 2, 2026, Today’s date October 2, 2026) on the example date Friday, October 2, 2026: Her puppies are due about November 6, 2026, between October 30, 2026 and November 13, 2026.

## Inputs

| Key | Label | Description |
| --- | --- | --- |
| from | The date I know | Which event the date is: the first breeding, the LH surge or progesterone rise, ovulation, or the first day of diestrus. |
| d | Date of that event | The day of the first breeding (mating), LH surge, ovulation, or first day of diestrus. |
| on | Today’s date | The day to count from, to show how far along the pregnancy is. |

## Outputs

| Key | Label | Description |
| --- | --- | --- |
| due | Estimated due date | The middle of the normal whelping window. |
| earliest | Earliest normal due date | The event date plus the shortest normal gestation. |
| latest | Latest normal due date | The event date plus the longest normal gestation. |
| days | Days along | Whole days from the event date to today’s date. |
| left | Days to the estimated due date | Whole days from today’s date to the estimated due date; negative once it has passed. |
| stage | Where she is now | The stage on today’s date, in one line. |
| ultrasound | Ultrasound check from | Day 25 after the event date, when Merck says ultrasound works best. |
| xray | X-ray puppy count from | Day 45 after the event date, when the puppies’ skeletons show on X-ray. |

## Method

Due date = event date + the middle of Merck’s gestation window: 65 days from the first breeding (58 to 72), 65 from the LH surge (64 to 66), 63 from ovulation (62 to 64), 57 from the first day of diestrus (56 to 58).

## Assumptions

- Gestation lengths are from the Merck Veterinary Manual; the estimate is the middle of each window.
- Days are counted from the event date as day 0; ultrasound from day 25 and X-ray from day 45 count from the same date.
- Breed, the number of litters and the litter size also change the length, so a vet check is the final word.

## Worked examples

1. from = breeding, d = 2026-03-01, on = 2026-04-05 gives due = 2026-05-05, earliest = 2026-04-28, latest = 2026-05-12, days = 35, left = 30, ultrasound = 2026-03-26, xray = 2026-04-15. Source: Merck Veterinary Manual, Whelping and Queening in Bitches and Queens (58–72 days from the first breeding), https://www.merckvetmanual.com/management-and-nutrition/management-of-reproduction-dogs-and-cats/whelping-and-queening-in-bitches-and-queens.
2. from = lh, d = 2026-12-20, on = 2027-02-21 gives due = 2027-02-23, earliest = 2027-02-22, latest = 2027-02-24, days = 63, left = 2. Source: Merck Veterinary Manual, Breeding Management of Bitches (parturition 64–66 days after the LH peak), https://www.merckvetmanual.com/management-and-nutrition/management-of-reproduction-dogs-and-cats/breeding-management-of-bitches.
3. from = ovulation, d = 2028-01-01, on = 2028-03-10 gives due = 2028-03-04, earliest = 2028-03-03, latest = 2028-03-05, days = 69, left = -6. Source: Merck Veterinary Manual, Approximate Gestation Periods (dog 62–64 days from ovulation), https://www.merckvetmanual.com/multimedia/table/approximate-gestation-periods.
4. from = diestrus, d = 2026-06-10, on = 2026-06-10 gives due = 2026-08-06, earliest = 2026-08-05, latest = 2026-08-07, days = 0, left = 57. Source: Merck Veterinary Manual, Whelping and Queening in Bitches and Queens (56–58 days from the first day of diestrus), https://www.merckvetmanual.com/management-and-nutrition/management-of-reproduction-dogs-and-cats/whelping-and-queening-in-bitches-and-queens.

## FAQ

### How long is a dog pregnant?

About 63 days from ovulation. The Merck Veterinary Manual gives 62 to 64 days from ovulation, 64 to 66 days from the LH surge, 56 to 58 days from the first day of diestrus, and 58 to 72 days from the first breeding.

### Why is the window so wide from the breeding date?

Sperm can live for days in the female, and a female may accept the male several days before she ovulates. So the breeding date says little about the day the eggs were fertilized. A vet can time ovulation with progesterone or LH tests, which narrows the window to 3 days.

### How is the due date worked out?

The calculator adds the middle of the normal window to your date: 65 days from the first breeding, 65 from the LH surge, 63 from ovulation, or 57 from the first day of diestrus. The earliest and latest dates add the ends of the window.

### When can a vet confirm that my dog is pregnant?

Merck says ultrasound works best from day 25 to day 35, and may miss a pregnancy before day 21. A relaxin blood test works after day 22 to 27. The puppies’ skeletons show on a routine X-ray from about day 42 to 45, and an X-ray after day 55 is best to count them.

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

Call your vet. A dog that is past the end of the normal window, or that strains for a long time without a puppy, needs a check.

### Does the litter size change the due date?

It can. Merck notes that breed, the number of litters she has had, and litter size all change the length of the pregnancy a little.

## Sources

- Merck Veterinary Manual, Whelping and Queening in Bitches and Queens (Davidson, updated June 2025): normal gestation 56–58 days from the first day of diestrus, 64–66 days from the progesterone rise or LH surge, 58–72 days from the first breeding. https://www.merckvetmanual.com/management-and-nutrition/management-of-reproduction-dogs-and-cats/whelping-and-queening-in-bitches-and-queens (retrieved 2026-10-02)
- Merck Veterinary Manual, Breeding Management of Bitches (Davidson and Carnevale, updated July 2025): parturition 64–66 days after the LH peak; due dates 56–58 days after the first day of diestrus. https://www.merckvetmanual.com/management-and-nutrition/management-of-reproduction-dogs-and-cats/breeding-management-of-bitches (retrieved 2026-10-02)
- Merck Veterinary Manual, Approximate Gestation Periods (dog 62–64 days from ovulation). https://www.merckvetmanual.com/multimedia/table/approximate-gestation-periods (retrieved 2026-10-02)
- Merck Veterinary Manual, Pregnancy Determination in Bitches and Queens (updated January 2026): ultrasound best at 25–35 days; relaxin after 22–27 days; skeletons on X-ray from about day 42–45. https://www.merckvetmanual.com/management-and-nutrition/management-of-reproduction-dogs-and-cats/pregnancy-determination-in-bitches-and-queens (retrieved 2026-10-02)