Dog heat cycle calculator
Estimate her next heat and fertile window from the day her last season began.
Leave blank to use the typical 180-day average.
Pick the date her last season began to see the estimate.
- When her next heat is likely to start
- The fertile window within it
How the dog heat cycle works
An intact female dog's reproductive cycle moves through four phases. Days are counted from the first day of proestrus, and vary from dog to dog.
Proestrus
Days 0–8Swelling and a bloody discharge begin. She's attracting males but not yet receptive.
Estrus
Days 9–17The fertile, receptive window. Ovulation usually falls around days 11–14.
Diestrus
Day 18–~70Signs settle down whether or not she's pregnant.
Anestrus
~70 days until the next heatThe quiet resting phase between cycles.
Breeds whose first season comes early
Small breeds tend to have their first heat sooner than large ones.
Frequently asked questions
How often do dogs go into heat?
Most dogs come into season about every six months, roughly 180 days. Smaller breeds can cycle more often, and large or giant breeds sometimes only once a year. If you know your dog's own interval, use it.
How long does a dog's heat last?
The visible heat (proestrus and estrus) usually runs two to three weeks, with the fertile window roughly in the middle.
When is a dog most fertile?
Usually during estrus, around days 9–17 after heat begins, with ovulation often near days 11–14.
Can I use this to plan or avoid breeding?
Only as a rough guide. To plan breeding or confirm timing, ask your vet about progesterone tests, which are far more accurate than a calendar estimate.
Kintail
Keep the whole tale
Kintail keeps your dog's growth, heat cycles, health records and daily notes in one place.
Track this for your dog →