Dog pregnancy calculator
A dog gives birth 58 to 72 days after the first mating, so a due date worked out from a mating date is a two-week window rather than a single day. If a vet timed ovulation with blood tests, the window tightens to 64 to 66 days after the LH surge.
A cat is more predictable: 64 to 66 days from mating. Switch between dog and cat below.
- days from the first mating, for a dog
- 58 to 72days from the first mating, for a dog
- days from the LH surge, for a dog or a cat
- 64 to 66days from the LH surge, for a dog or a cat
- every figure from the Veterinary Manual
- Merckevery figure from the Veterinary Manual
Pregnancy calculator
Puppies due between
Dec 7, 2026 and Dec 21, 2026
That is a window of 15 days, counted from the first mating.
The dog window is wide because a mating date is not a conception date. Merck puts birth at 58 to 72 days from the first breeding, but only 64 to 66 days from the LH surge, which a vet can measure.
Today is day 6 of the count.
Estimate only. For health questions, ask your vet.
What happens when
Every date below comes from a published figure. Anything we could not source is left out rather than guessed.
Day 18
The embryos settle into the uterus
Wed, Oct 28, 2026
Merck puts implantation at about 18 days in the dog.
Day 21
Small swellings can be felt
Sat, Oct 31, 2026
Swellings along the uterine horns appear at about 21 days. Before 21 days an ultrasound scan can wrongly come back negative.
Day 22 to 27
A blood test can confirm it
Sun, Nov 1, 2026 to Fri, Nov 6, 2026
A commercial relaxin assay can detect pregnancy after 22 to 27 days.
Day 25 to 35
Best window for an ultrasound scan
Wed, Nov 4, 2026 to Sat, Nov 14, 2026
Merck says the scan is best performed at 25 to 35 days.
Day 42 to 48
Puppy skeletons show on an x-ray
Sat, Nov 21, 2026 to Fri, Nov 27, 2026
Fetal bone is not visible on a routine x-ray until about day 42 to 45, and is quite prominent by day 47 to 48.
Day 55
Counting the litter
Fri, Dec 4, 2026
An x-ray after day 55 is the best way to work out how many puppies to expect.
Day 58 to 72
The birth window
Mon, Dec 7, 2026 to Mon, Dec 21, 2026
Counted from the first mating, birth falls anywhere from day 58 to day 72. A drop in rectal temperature usually comes 8 to 24 hours before whelping.
In short
Key takeaways
- From a mating date, a dog due date is a window of about 15 days. Nobody can give you one day from that information.
- From a vet-timed LH surge, the window is 3 days. That is the only way to get a precise date.
- A cat due date from mating is already tight, at 64 to 66 days.
- A temperature drop 8 to 24 hours before whelping is the clearest short-notice signal.
- Every date here comes from the Merck Veterinary Manual. Milestones we could not source are left out, not guessed.
The confusion
Three ways to count, three answers
| Counted from | Length | How you would know the date |
|---|---|---|
| The first mating | 58 to 72 days | You watched it happen. Easy to know, but the least precise starting point. |
| The LH surge or progesterone rise | 64 to 66 days | A vet measured it with blood tests before the mating. |
| The first day of diestrus | 56 to 58 days | A vet identified it from vaginal cytology. |
Merck on the dog: "58-72 days from the first instance that the female permitted breeding" and "64-66 days from the initial rise in progesterone from baseline (generally > 2 ng/mL) or the luteinizing hormone (LH) surge".
Scroll the table sideways to see every column.
Why
Why the dog window is so wide
A dog can accept a male for a week or more, and the fertile part of that is not the same for every dog. Sperm survives for several days inside the female, so a mating on Monday can produce a conception on Thursday. The pregnancy itself is a fairly fixed length; it is the starting line that moves.
The Merck manual puts it bluntly: “Breeding dates and conception dates do not correlate closely enough to permit accurate prediction of whelping dates”. Any tool that gives you a single date from a mating date is presenting a guess as a fact.
In the cat none of that applies in the same way, because ovulation is triggered by mating. The surge and the mating happen together, which is why a cat due date is tight.
15 days
the honest width of a dog due window worked out from a mating date
Cats
Cat pregnancy
Merck gives one figure for the queen: birth comes 64 to 66 days from the LH surge, and that surge is triggered by copulation. Setting the calculator to cat uses those numbers.
The milestone list for cats is shorter than the dog one on purpose. Implantation is given separately for the cat, at about 14 days against 18 in the dog. The scanning and x-ray windows on the Merck page are given for dogs and cats together, so we show those and leave out anything stated for dogs alone.
Limits
What this tool will not tell you
It gives dates. It does not give advice on feeding a pregnant dog or cat, on what is normal during labour, on when something has gone wrong, or on what to do if it has. Those are questions for a vet who can see the animal.
If you are breeding deliberately, have your vet involved before the mating rather than after. That is also the only route to a precise due date.
FAQ
Questions people ask
- How long is a dog pregnant?
- Counted from the first mating, the Merck Veterinary Manual gives 58 to 72 days. Counted from the LH surge, which a vet measures with blood tests, it is a much tighter 64 to 66 days. Both figures describe the same pregnancy; they just start the clock at different points.
- Why is the dog due date window two weeks wide?
- Because a mating date is not a conception date. Sperm can survive for several days in the female reproductive tract, and ovulation can happen before or after the mating. Merck says plainly that breeding dates and conception dates do not correlate closely enough to permit accurate prediction of whelping dates.
- How can I narrow the due date down?
- Have a vet time ovulation with progesterone or LH testing before the mating. That replaces the 14 day window with a 3 day one. It is the only way to get a precise due date, and it has to be done at the time rather than worked out afterwards.
- How long is a cat pregnant?
- 64 to 66 days. In cats the LH surge is triggered by mating itself, so the mating date and the hormonal start of the pregnancy are effectively the same day. That is why a cat due date window is three days wide while a dog one is fifteen.
- When can a vet confirm the pregnancy?
- A blood test for relaxin works after 22 to 27 days. An ultrasound scan is best at 25 to 35 days, and before 21 days it can wrongly come back negative. An x-ray does not show the skeletons until about day 42 to 45.
- How do I find out how many puppies to expect?
- An x-ray after day 55 is the best method, because by then the skeletons are clear enough to count. Ultrasound is good for confirming a pregnancy but poor at counting.
- Is there a sign that birth is close?
- A drop in rectal temperature, to a mean of 98.8F with a range of 98.1 to 100F, happens in most dogs 8 to 24 hours before whelping. Taking a twice-daily temperature in the last week is how breeders use that signal.
- What should I do as the due date approaches?
- Speak to your vet and have their out-of-hours number to hand. This calculator gives dates and nothing else. We do not give advice on care, on complications, or on the birth itself, because those are veterinary questions and the answers depend on the individual animal.
Method
How we calculate this
Every figure on this page is taken from the Merck Veterinary Manual pages listed below and checked against them on the date shown. Where Merck gives a range we show the range, and where it gives no figure we leave the milestone out. The method is written up in full on the how we calculate page.
Sources
3 sources behind the figures on this page.
Whelping and Queening in Dogs and Cats
Merck Veterinary Manual - read 2026-10-08
merckvetmanual.comBreeding Management of Dogs and Cats
Merck Veterinary Manual - read 2026-10-08
merckvetmanual.comPregnancy Determination in Dogs and Cats
Merck Veterinary Manual - read 2026-10-08
merckvetmanual.com
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Last reviewed . Estimate only. For health questions, ask your vet.