Dog Pregnancy Calculator: Due Date & Whelping Window

How it works

How to use the dog pregnancy calculator

Choose which date you actually have. A first mating date works, but the LH surge or progesterone date gives a much narrower window.
Enter the date. The tool shows the earliest, most likely and latest whelping dates and where today falls.
Download the calendar file to add all three dates to your phone, including a reminder to call your vet if nothing has happened by the latest date.
Book a vet check. Only your vet can confirm pregnancy and plan the due date with tests.

This is an estimate. It is not a diagnosis, and it cannot tell you whether your dog is pregnant.

The numbers

How long is a dog pregnant?

The Merck Veterinary Manual gives three ranges, depending on which date you count from. Counting from the first day she accepted breeding, gestation runs 58 to 72 days. Counting from the LH surge or the initial rise in progesterone (above about 2 ng/mL), it runs 64 to 66 days. Counting from the first day of diestrus, it runs 56 to 58 days.

Start date used	Window (Merck)	Our 'most likely'	Notes
First mating	58 to 72 days	65 days	Least precise; sperm survive for days
LH surge or progesterone rise	64 to 66 days	65 days	Most precise; needs vet testing
First day of diestrus	56 to 58 days	57 days	Needs vet cytology

Windows are the ranges quoted by the Merck Veterinary Manual. 'Most likely' is the midpoint of that range.

Why so wide from mating? Merck notes that breeding dates and conception dates do not correlate closely enough to predict whelping dates accurately. A female can accept a male before and after she ovulates, and the calculator cannot know when she did. If you plan breeding, ask your vet about progesterone testing.

Whelping signs

Signs that whelping is near

According to Merck, most dogs show a drop in rectal temperature, averaging 37.1°C (98.8°F) with a range of 36.7 to 37.8°C (98.1 to 100.0°F), 8 to 24 hours before whelping, following the fall in progesterone. Labor typically begins within 24 hours after serum progesterone drops below 2 ng/mL. Other changes such as loosening of the perineum, mammary engorgement and changes to the abdomen can occur, but Merck calls them neither sensitive nor specific.

When to call your vet. Call if the latest date in the window has passed with no labor, if she seems unwell, or if labor has started and puppies are not arriving. Merck warns against intervening too early, because preterm puppies cannot be managed effectively, and against waiting too long, which can lead to intrauterine fetal death. Your vet can tell you which side your dog is on.

Week by week

What owners ask on Reddit

Quotes are copied word for word from public Reddit threads. They are single people's accounts, not evidence, and we use them only to show the questions the tool is meant to answer.

“If this happened less than 3-4 weeks ago there isn't a reliable way to determine pregnancy. Not by behaviour, not by clinical assessment, not by bloods, not by ultrasound.”

r/AskVetAnimals, Feb 2026, an owner whose dog may have mated at a family barbecue · Reddit thread

Our take. This calculator works from a date you know: the first mating, the LH or progesterone rise, or the start of diestrus. If the mating was unplanned or very recent, the first step is a vet visit, not a due date. Once the date is confirmed, the due window is 58 to 72 days from first mating, narrower from the hormone dates.

“Vet here - you need at least 3 weeks before anything is visible via ultrasound.”

r/AskVetAnimals, same thread, a comment from a user who says they are a vet · Reddit thread

Our take. That fits the first answer: pregnancy is confirmed by a vet, not by the calculator. We cannot verify who posted this, so we use it only to explain why the tool asks for a known date.

Questions

Frequently asked questions

How long are dogs pregnant?

From first breeding, 58 to 72 days. From the LH surge or progesterone rise, 64 to 66 days. From the first day of diestrus, 56 to 58 days. These ranges are from the Merck Veterinary Manual.

Is 63 days the right number?

You will often see 63 days quoted. Merck's ranges are wider because dogs ovulate at different times in the heat cycle. If you know the LH surge or progesterone date, the central figure is about 65 days.

How can I tell my dog is going into labor?

A drop in rectal temperature 8 to 24 hours before whelping is the best-known sign, with an average of 37.1 C (98.8 F). Other changes occur but are not reliable.

What if my dog goes past the latest date?

Call your vet that day. Merck warns that waiting too long can lead to fetal death, so a check is better than watching and waiting.

Can a calculator confirm she is pregnant?

No. Only a vet can confirm pregnancy, usually with an exam, ultrasound or blood test.

Why do other calculators show a single day?

Many simply add a fixed number of days, often 63 or 65, to the mating date. Merck's ranges show that dogs vary, so we show the full window.

Keep going

More tools for your pet

ToolPuppy weight calculatorTrack growth after birth.ToolDog calorie calculatorPregnancy feeding estimate.ToolDog age calculatorConvert dog years to human years.

Sources

Where the numbers come from

Merck Veterinary Manual, Whelping and Queening in Dogs and Cats — gestation ranges, temperature drop, progesterone
AAHA 2021 Nutrition and Weight Management Guidelines, energy requirement box — gestation factor 3.0 for the last 21 days (dogs)

This calculator is for planning only and does not replace veterinary care. Last reviewed October 2026.

Dog Pregnancy Calculator: Due Date and Whelping Window

🐶Dog due date calculator