Dog Heat Cycle Calculator
Everything is calculated in your browser. The dates you enter are never sent anywhere — no signup, no account, nothing stored.
The four stages in plain English
Proestrus (about 9 days): bleeding and a swollen vulva; males are interested, she is not receptive yet. Estrus (about 9 days): she is receptive — this is when ovulation happens and breeding can take. Diestrus (about 2 months): the body behaves as if pregnant whether she is or not, which is why false pregnancies happen. Anestrus: the quiet months until the next heat. The full walkthrough is our dog heat cycle stages guide.
When breeding can happen
Only during estrus, and within it, most often around days 9–14 of the heat. But “most often” hides a lot of individual variation — some females ovulate on day 7, others past day 20 — and a mating a few days early or late still takes, because sperm survive for days. If the timing really matters (a stud fee, a long drive, a planned litter), progesterone blood tests at your vet beat every calendar, including this one.
How often dogs come into heat
About every six months on average — but the honest range is every 5 to 11 months. Smaller breeds often cycle more often; giant breeds may cycle only once a year. Her own history is the best predictor, which is why the calculator above lets you enter her usual cycle length if you know it.
From heat to due date
If she is bred in the estimated fertile window, the projected due date above is simply breeding day + 63 — clearly labeled a projection, because both the heat and the breeding day are estimates. Once a real mating happens, switch to the dog pregnancy calculator with the actual first mating date; once you have a progesterone-timed ovulation date, the from-ovulation calculator is tighter still.
Frequently asked questions
How often do dogs come into heat?
Most dogs cycle about every six months, but the normal range is wide — roughly every 5 to 11 months. Small breeds often cycle more frequently and giant breeds less. The first heat usually arrives between 6 and 24 months of age, depending on size and breed.
When in the heat cycle can a dog get pregnant?
During estrus, the second stage, when she is receptive and ovulation happens. That is commonly around days 9–14 of the cycle, but individual timing varies a lot — which is why breeders who need precision use progesterone testing rather than counting days alone.
How long does a heat cycle last?
The visible heat — proestrus plus estrus — lasts about 2–3 weeks in total, roughly 9 days per stage on average. The full cycle including diestrus and the quiet anestrus period runs to the next heat, typically around six months later. Each of the four stages is explained in full in our guide to the dog heat cycle stages.
Can this calculator tell me the exact breeding day?
No calculator can. It estimates the fertile window from averages so you can plan vet visits and progesterone tests, which are what actually pin down ovulation. Once you have an ovulation date, our from-ovulation pregnancy calculator gives the tightest due date on the site.
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One toolkit for the whole breeding journey — each calculator does one job properly: