CollarDog Heat Cycle Calculator: Next Season & Fertile Window
Track your dog's heat cycle. Estimate when her next season is due and when her fertile window falls, from the start date of her last heat and her breed size. Planning a breeding? A dog ovulation calculator sits right below to time the best mating days.
Dog Heat Cycle Calculator
Enter the start of her last heat to estimate her cycle.
How the Dog Heat Cycle Works
A dog's reproductive cycle, or "season", moves through distinct phases. Knowing where she is helps you plan a breeding or simply prepare for her next heat.
The Four Phases
- Proestrus (about days 1 to 9): bleeding begins and her vulva swells, but she is not yet receptive to males.
- Estrus (about days 9 to 18): the fertile phase. She is receptive and can become pregnant; the most fertile days are usually days 9 to 15.
- Diestrus (about 2 months): the fertile window closes, whether or not she is pregnant.
- Anestrus: the resting phase between cycles, until the next season.
Canine Heat Cycle: How Often She Cycles
Most dogs come into heat about every 6 months, but this depends on breed size, so this calculator adjusts the interval accordingly.
Note the start of her heat
Record the first day you saw bleeding or swelling.
Add her breed size
Cycle length varies between small and giant breeds.
See her cycle
Get her next expected season and the fertile window of this heat.
Dog Ovulation Calculator: Find the Fertile Window
Planning a mating? Estimate her ovulation day and best breeding days from the first day of her heat.
Dog Ovulation Calculator
Enter the first day of her heat to estimate the fertile window.
How Dog Ovulation Timing Works
A dog's fertile window opens during the estrus phase of her heat. Counting from the first day she started bleeding (proestrus), ovulation usually happens around day 11, within a natural range of about days 9 to 15.
The eggs need roughly two days to mature after ovulation, so the best mating days are typically days 11 to 13. Many breeders mate every other day across this window.
Estimated ovulation ≈ first day of heat + 11 days
Why This Is Only an Estimate
Dogs do not all ovulate on the same day, and some have silent or irregular heats. That is why the result is shown as a window, and why a vet's progesterone test is the only reliable way to time a breeding.
Note the first day of heat
Record the day bleeding first appeared (start of proestrus).
Read the fertile window
See the estimated ovulation day and best breeding days.
Confirm with your vet
Use a progesterone test to pinpoint the real ovulation date.
Frequently Asked Questions
Answers to the most common questions about the canine heat cycle, ovulation, and breeding timing.
Most dogs go into heat about twice a year, roughly every 6 months. Small breeds may cycle more often (every 4 to 6 months), while some giant breeds cycle only once a year. A young dog's cycle can be irregular during her first year or two.
A visible heat lasts about 2 to 4 weeks. It has two main phases: proestrus (roughly the first 9 days, with bleeding but she is not yet receptive) and estrus (roughly days 9 to 18, when she can become pregnant).
A dog is usually most fertile during the estrus phase, around days 9 to 15 after the start of her heat, though this varies from dog to dog. The only reliable way to pinpoint the fertile window and ovulation is progesterone testing at your vet.
Yes. Small breeds tend to come into heat more frequently, sometimes every 4 to 6 months. Medium and large breeds usually cycle about every 6 to 7 months. Giant breeds often cycle only once every 12 months.
A canine heat cycle calculator estimates when a dog's next season is due and where her fertile window falls. You enter the first day of her last heat and her breed size, and it applies the average canine cycle interval to project the next one. Only a progesterone test at your vet can confirm ovulation.
A dog usually ovulates around day 11 of her heat, counting from the first day of proestrus (the start of bleeding), though it can naturally range from about day 9 to day 15. Because this varies from dog to dog, a progesterone test at your vet is the only reliable way to confirm ovulation.
The best breeding days are usually around days 11 to 13 of the heat, a couple of days after ovulation, once the eggs have matured. Many breeders mate every other day across this window to improve the chances of conception.
A calendar estimate is only a rough guide. Individual dogs ovulate on different days, and silent or irregular heats are common. For a real breeding decision, a progesterone test (and sometimes vaginal cytology) at your vet is the only reliable way to pinpoint ovulation.
Yes. Counting from the first day of heat, ovulation usually falls around day 11, and the best breeding days are roughly days 11 to 13. Many breeders mate every other day across that window. This calculator applies that canine breeding chart to your dog's dates, but a progesterone test remains the only reliable confirmation.
Sources & Further Reading
The cycle and ovulation figures on this page reflect published veterinary averages. To go deeper, visit these trusted references: