How to use the dog pregnancy calculator
Step 1 — Choose your date type. Most owners use the mating date. If your vet tracked an LH surge or ovulation, those dates can be more precise.
Step 2 — Enter the date. The calculator applies the standard 58–68-day delivery window (average 63 days from mating).
Step 3 — Select breed size (optional). Small breeds often whelp around day 62; large breeds around day 64.
Step 4 — Review the timeline. See current week, development notes, and labor signs. Confirm any concerns with your veterinarian.
Gestation formulas
- Average due date = mating date + 63 days
- Earliest delivery = mating date + 58 days
- Latest delivery = mating date + 68 days
- LH surge due date = LH date + 65 days
- Ovulation due date = ovulation date + 63 days
Understanding your due-date window
Why the window spans 10 days rather than a single date. Unlike a fixed incubation period, canine gestation length varies by individual dog and depends on precisely when ovulation occurred relative to mating — sperm can remain viable in the reproductive tract for several days, so mating date and conception date aren't always the same day. This is exactly why a mating-date estimate returns a range rather than a single confident day.
LH and ovulation timing narrow the window considerably. If your vet tracked a luteinizing hormone (LH) surge or confirmed ovulation via progesterone testing during a planned breeding, that date anchors gestation length far more precisely than the mating date alone — this is standard practice for breeders managing a planned litter, since it also helps confirm true labor onset versus false alarms.
Breed size shifts the typical delivery day within the window. Smaller breeds often whelp a day or two earlier than the 63-day average, while larger breeds trend a day or two later — a modest effect, but worth factoring in when deciding how closely to monitor as the estimated date approaches.
What to do as the window opens. Begin close monitoring (temperature checks twice daily) starting a few days before the earliest estimated date — a drop below 99°F (37.2°C) reliably precedes labor onset by roughly 24 hours in most dogs, making it a more actionable signal than the calendar date alone.
Week-by-week dog pregnancy stages
Week 1 (days 1–7) — Fertilization
Fertilization occurs. Sperm meets egg and embryos begin cell division. No visible signs yet. Sperm can survive in the reproductive tract up to 7 days.
Week 2 (days 8–14) — Blastocyst formation
Zygotes divide repeatedly into blastocysts. Still no visible physical changes in the mother.
Week 3 (days 15–21) — Implantation
Blastocysts implant into the uterine wall (around days 18–21). Relaxin hormone production begins. Signs may include lethargy, tender nipples, morning sickness, and appetite changes.
Week 4 (days 22–28) — Heartbeat detectable
Heartbeats detectable via ultrasound. A vet can confirm pregnancy. Organs and facial features begin forming. Morning sickness may peak — feed bland food if vomiting.
Week 5 (days 29–35) — Visible weight gain
Fetuses develop gender organs. Belly starts to round and weight gain becomes noticeable. Increase food intake. Eyes begin forming.
Week 6 (days 36–42) — Nipple changes
Nipples darken and enlarge. Puppies develop skin pigment. Switch to high-quality puppy food and increase intake by about 35–50% above normal.
Week 7 (days 43–49) — Prepare whelping area
Puppy hair begins growing. Abdomen drops lower. Prepare a quiet whelping box, limit strenuous exercise, and keep the mother away from other animals.
Week 8 (days 50–56) — Nesting begins
Mother may start nesting. Colostrum production begins. You may see puppies moving in the belly. A vet X-ray around day 45 can estimate litter size.
Week 9 (days 57–63+) — Final week & labor
Appetite may reduce. Temperature below 99°F (37.2°C) signals labor within 24 hours. Labor signs include panting, shivering, restlessness, and contractions. Contact your vet if no birth by day 68.
Pregnancy signs & labor checklist
Early & mid-pregnancy signs
- Decreased appetite (first few weeks)
- Nipple swelling and darkening
- Weight gain (noticeable from week 5)
- Morning sickness / vomiting (weeks 3–5)
- Lethargy and behavior changes
- Belly enlargement (visible from week 6)
- Nesting behavior (week 8+)
- Temperature drop below 99°F — labor imminent
Labor signs
- Body temperature drops below 99°F — labor within 24 hours
- Restlessness and nesting
- Loss of appetite
- Panting and shivering
- Visible abdominal contractions
- Stage 1 labor lasts 6–12 hours before active delivery
