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FurCalc

Dog Gestation Calculator — Progesterone, LH Surge & Mating-Based Whelping Date

A breeder-focused calculator that supports the three reference points reproductive veterinarians use to predict whelping: day of ovulation (progesterone ≈ 5 ng/mL), LH surge day, or first confirmed mating. Tightest accuracy (±1 day) comes from progesterone timing; mating-date alone carries ±5 days of error. The framework follows the AKC canine reproduction guide.

Calculator

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Reference timing method
Expected whelping
July 18, 2026
Window: July 17, 2026 – July 19, 2026
Day
0 / 63
Week
1
Trimester
1

Breeder checklist

Ultrasound (confirm + heart count)
Day 28 — June 13, 2026
X-ray (count skeletons)
Day 45+ — June 30, 2026
Whelping box setup
July 11, 2026
Begin temperature monitoring
July 17, 2026
Progesterone-based timing is the gold standard for breeders. Consult your reproductive veterinarian for serial progesterone testing.

Why progesterone timing beats mating-date timing

Canine reproduction is unusual in several ways: bitches are monoestrous (one heat every 6–12 months), they can mate days before or after ovulation, and oocytes require 2–3 days of maturation before fertilization is possible. These facts make the mating date a relatively loose proxy for conception.

Veterinarians instead use serial progesterone (P4) testing through the heat cycle to pinpoint ovulation — the true biological zero for gestation. At LH surge P4 is approximately 2 ng/mL; ovulation occurs 2 days later at approximately 5 ng/mL. From ovulation, whelping occurs within 63 ± 1 days.

Elective cesarean planning

Brachycephalic (short-nosed) breeds such as French Bulldogs, English Bulldogs, Pugs, and Boston Terriers have caesarean rates of 80–95 % due to narrow dam pelvis relative to puppy skull size. Elective C-sections are typically scheduled for day 61–62 from LH surge (or day 59 from ovulation) to balance fetal lung maturity (high at day 58+) against the risk of dystocia.

Temperature-drop monitoring

Starting day 58 post-ovulation, take rectal temperature twice daily (morning and evening). A sustained drop below 99°F (37.2°C) predicts stage-1 labor within 12–24 hours. Gather your whelping kit and clear your schedule when this drop occurs.

Progesterone vs LH surge vs mating date: which timing reference?

ReferenceWhelping windowAccuracyCost
Day of ovulation (P4 ≈ 5 ng/mL)+63 days±1 day$60-120 (3-4 P4 draws)
LH surge day+65 days±2 days$80-150 (LH + P4 draws)
First mating date+58 to +68 days±5 daysFree
Last mating date+56 to +66 days±5 daysFree

Frequently Asked Questions

What is the most accurate way to predict whelping date?

Progesterone testing. Ovulation occurs when P4 reaches ~5 ng/mL. Whelping is 63 ± 1 days from ovulation. Mating-date-based calculations carry ±5 days of uncertainty.

What is the difference between mating date and ovulation date in dogs?

A female dog can mate before or after ovulation because sperm survives 5–7 days in the reproductive tract. Ovulation is the more precise reference for gestation.

When does progesterone hit 5 ng/mL in the breeding dog?

This is ovulation day. Before ovulation P4 is <1 ng/mL. It begins rising 2 days before ovulation (at LH surge, P4 ~2 ng/mL) and reaches ~5 ng/mL at ovulation.

Can a dog whelp before 58 days?

Puppies born before day 58 from LH surge (equivalent to day 56 from ovulation) are premature and may not have lung surfactant developed. Contact your repro vet immediately.

Why is temperature monitoring important?

A rectal temp drop below 99°F (37.2°C) indicates progesterone decline and labor within 12–24 hours. Starting monitoring at day 58 post-ovulation is standard.

How do I estimate litter size?

An x-ray taken at day 45+ shows calcified fetal skeletons and allows an accurate count. Breed and dam size correlate — toy breeds 1–3, small 4–6, medium 4–8, large 6–10.

What is a C-section rate in breeds like French Bulldogs?

Brachycephalic breeds (Bulldogs, French Bulldogs) have cesarean rates above 80 % due to narrow pelvis. These litters should be delivered in clinic by elective C-section on day 61–62 from LH surge.

How do I know when my bitch is in stage-1 labor?

Signs include restlessness, panting, nesting, temperature drop below 99°F, and refusal of food. Stage 1 lasts 6–12 hours before visible contractions (stage 2).

Sources & References

  1. [1]
    Canine Reproduction: Progesterone Timing — Society for Theriogenology
  2. [2]
    Ovulation Timing in the Bitch — Royal Canin Veterinary Focus
  3. [3]
    Managing Canine Parturition — Today's Veterinary Practice