Why there is not one guaranteed number
A commonly quoted figure is about 63 days, but what matters is the starting point. Merck Veterinary Manual describes approximately 62–64 days from ovulation, compared with a much wider 58–72 days from the first mating. Sperm survival and variation in breeding relative to ovulation explain why a mating date is a less precise marker.
Which date should I enter?
Choose the reference you actually know, rather than guessing. If only a mating date is recorded, select that in the Dogiie pregnancy calculator. Use LH, progesterone, ovulation or diestrus modes only when your veterinarian has confirmed the exact clinical event.
Can breed change the due date?
Breed alone does not justify adjusting the calculator’s medical gestation interval. Some breeds face additional birthing risks, so breed may affect the veterinary birth plan—not an automatic extra number of pregnancy days.
When are dates not enough?
When pregnancy is unconfirmed, a dog is ill, or labor appears abnormal, a date estimate should not delay veterinary examination. Also, if a recorded date is incorrect, even a carefully coded calculator will be wrong.
Source: Merck Veterinary Manual — Whelping and Queening. This information is not individual medical advice.