Our dog pregnancy calculator counts whole days from the date you enter and applies the gestation ranges published in veterinary references. This page shows every rule it uses, so you can check the numbers yourself.
Due date methods
| You enter | Due date | Normal range | Flagged as overdue after |
|---|---|---|---|
| First mating date | Day 63 | Day 58 to 72 | Day 72 |
| Ovulation date (progesterone test) | Day 63 | Day 62 to 64 | Day 64 |
| LH surge date | Day 65 | Day 64 to 66 | Day 66 |
| First day of diestrus | Day 57 | Day 56 to 58 | Day 60 |
| Vet estimate (unknown mating date) | Day 63 from the estimated start | Day 56 to 70 | Day 72 |
Counting from the mating date gives a wide window because sperm can survive for 7 days or more and the mating day is often not the day of fertilization. Hormone dates (ovulation, LH surge, diestrus) narrow the window to a day or two. When she mated more than once, we count from the first mating, the same date vets use to judge whether a pregnancy is overdue.
Key dates we show
| Milestone | Timing |
|---|---|
| Embryos implant | About day 18 |
| Relaxin blood test | From about day 22 to 27 |
| Ultrasound (best time) | Day 25 to 35 |
| Puppy bones visible on X-ray | From about day 42 to 45 |
| X-ray puppy count | After day 55 |
| Start temperature checks | Day 55, two to three times a day |
Temperature checker rules
- Normal: about 100 to 102.5°F (37.8 to 39.2°C).
- Below 99°F (37.2°C): labor usually starts within 8 to 24 hours.
- A drop that lasts more than 24 hours with no labor: call your vet.
- 103°F or higher: possible fever, call your vet.
Temperature readings you log are stored only in your own browser. They are never sent to us.
Sources
- Merck Veterinary Manual: Whelping and Queening in Bitches and Queens
- Merck Veterinary Manual: Pregnancy Determination in Bitches and Queens
- Veterinary Practice News: Dog reproductive emergencies identified
- UC Davis School of Veterinary Medicine: Dystocia in the Bitch
- Cornell University College of Veterinary Medicine: Dystocia in dogs
- Purdue University: What to Expect When Your Dog is Expecting
- Today’s Veterinary Practice: Fetal count radiology
These figures were last checked on November 12, 2026. Estimates only, not veterinary advice.