Enter the day your dog's last season began and we'll estimate when her next heat is due — and the fertile window within it. Estimates only; every dog is different.
Most dogs come into season roughly every six months (about 180 days). Smaller breeds can cycle more often, and large or giant breeds sometimes only once a year — so use your dog's own interval if you know it.
The visible heat — proestrus plus estrus — usually runs about two to three weeks, with the fertile window falling roughly in the middle.
Usually during estrus, around days 9–17 after heat begins, with ovulation often near days 11–14. This calculator highlights that estimated window.
Treat it as a rough guide only. For breeding or to confirm timing, your vet can run progesterone tests, which are far more accurate than calendar estimates.