Enter the first day of her heat to estimate when she’ll ovulate and the best days to breed, for natural mating, chilled or frozen semen.
Disclaimer: Calendar estimates can’t confirm ovulation or guarantee pregnancy. Progesterone testing by your vet is the reliable way to time breeding.
The calculator counts from the first day of her heat (day 1) and uses average timing. Proestrus lasts about 9 days on average, and the LH surge, the hormone surge that triggers ovulation, usually comes near its end. Ovulation follows 2–3 days after the LH surge, and the eggs need another 2–3 days to mature (Merck Veterinary Manual).
So for an average dog, the LH surge comes around day 9, ovulation around days 11–12, and the best natural breeding days are around days 12–15. That’s the window this calculator shows, adjusted for the type of breeding you choose.
| Breeding type | Days after LH surge | Average heat day |
|---|---|---|
| Natural mating or fresh semen | Days 3–6 (two breedings) | About days 12–15 |
| Chilled semen | Days 4 and 6 (or 3 and 5) | About days 13 and 15 |
| Frozen semen | Day 5 or 6 | About days 14–15 |
Source: Merck Veterinary Manual. Fresh semen can survive in the female for 9 days or more, which is why matings a few days early can still result in pregnancy.
Proestrus can last anywhere from 3 days to 3 weeks, so some dogs ovulate much earlier or later than average. Lighter discharge and a dog that “flags” her tail are helpful signs, but they don’t pinpoint ovulation.
On average, around days 11–12 after the first sign of heat. But it varies widely, because proestrus can last 3 days to 3 weeks. Progesterone testing is the only reliable way to know.
Not quite. Dog eggs need 2–3 days to mature after ovulation, so the best days for natural breeding are about 3–6 days after the LH surge, which is 1–4 days after ovulation.
For natural or fresh-semen breeding, two breedings about 2 days apart within the fertile window are usually advised.
It's unlikely, because ovulation usually comes later. But sperm can survive for 9 days or more, so a mating early in heat can sometimes still lead to pregnancy.
Due date, pregnancy week and a dated timeline from the mating date.
Open calculator →Predict her next heats and the typical fertile days.
Open calculator →Turn your vet's progesterone results into breeding dates.
Open calculator →Countdown to labor, prep checklist and a puppy delivery log.
Open calculator →The right box size for your dog, with a layout diagram.
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Open calculator →Weaning, deworming, vaccines and go-home dates.
Open calculator →How many puppies to expect for her size.
Open calculator →Sources: Merck Veterinary Manual – Breeding Management of Dogs and Cats. This page is general information, not veterinary advice. Read our veterinary disclaimer.