Dog Heat Cycle Calculator & Tracker
Log the first day of each season. The tracker shows where she is in her cycle today, a rough window when she's likely to be receptive, and when her next heat is due, using her own history once you've logged two or more heats.
Her heat log
Saved in this browserNo heats logged for this dog yet.
Log at least one heat start date to see her stage today and the next predicted season.
How the heat predictions are calculated
With one logged heat, the next one is projected at the average interval of 7 months that the Merck Veterinary Manual gives, with a wide window because normal intervals run from 4 to 13 months (large breeds such as Great Danes may cycle every 9–12 months). Once you log two or more heats, the tracker switches to her own average gap and narrows the window to her own variation, never tighter than ±14 days.
The stage-today estimate uses Merck's average stage lengths: proestrus about 9 days, estrus about 9 days, diestrus about 2 months. Real dogs vary a lot (estrus can be 3 days or 3 weeks), so the "likely receptive" window is a planning aid for when to book progesterone tests, not a fertility prediction.
Want the biology behind the stages? The dog heat cycle guide has an interactive stage explorer. Planning a litter? Once she's bred, move to the dog pregnancy calculator.
Questions breeders ask
How often do dogs go into heat?
Usually about twice a year. The Merck Veterinary Manual gives an average interval of 7 months, with a normal range of 4 to 13 months; some large breeds cycle every 9–12 months.
How long is a dog in heat?
The visible heat is proestrus plus estrus. Merck gives about 9 days for each on average, so roughly two to three weeks in total, but either stage can be as short as a few days or as long as three weeks.
When is a dog most fertile?
During estrus, around ovulation, which happens about 2–3 days after the LH peak (Merck). Because timing varies so much between dogs, vets use progesterone blood tests, usually every couple of days, to recommend breeding days.
Can I track more than one dog?
Yes. Add as many dogs as you like; each has its own log. Everything stays in your browser and the Clear all data button deletes it.