Dog Heat Cycle Calculator 2026
Predict your dog’s next heat cycle, track fertility windows, and plan breeding or spaying schedules with precision. Understand the 4 stages of the canine estrous cycle.
Dog Profile & Cycle History
Define your dog’s breed size, cycle history, and your primary goal
The first day you noticed physical signs of her last heat cycle
Average days between the start of one heat and the next (typically 180)
How long the bleeding and swelling typically last
Cycle & Fertility Estimates
Next heat, fertile window, and stage breakdown
Enter your dog’s cycle history and goals above, then click Predict Cycle & Fertility to reveal her personalized heat calendar.
Heat Cycle Patterns by Breed Size
General guidelines for canine estrous cycles. Individual dogs may vary, so tracking your dog’s specific history is the most accurate method.
| Breed Size | Average Interval | Heat Duration | First Heat Age |
|---|---|---|---|
| Small Breeds | 4 – 6 months | 14 – 21 days | 5 – 6 months |
| Medium Breeds | 6 months | 18 – 24 days | 6 – 8 months |
| Large Breeds | 6 – 8 months | 21 – 28 days | 8 – 12 months |
| Giant Breeds | 8 – 12 months | 21 – 28 days | 12 – 24 months |
Canine Reproduction FAQ
Learn more about the estrous cycle, fertility tracking, and safely managing your dog’s reproductive health.
A dog’s heat cycle (estrous cycle) typically lasts between 2 to 4 weeks. The entire cycle from one heat to the next averages 6 months (180 days), but this can range from 4 to 12 months depending on the breed and individual dog.
The cycle has four stages: Proestrus (swelling, bleeding, 7-10 days), Estrus (fertile window, discharge lightens, 5-9 days), Diestrus (post-fertile, 60-90 days), and Anestrus (resting phase, 3-4 months).
The most fertile period, called Estrus, usually begins around day 9 to 11 of the heat cycle. The vaginal discharge changes from dark red to a lighter, straw-colored pink, and the female will actively stand and “flag” her tail when touched.
Most dogs go into heat twice a year, or approximately every 6 months. However, small breeds may cycle three times a year, while giant breeds might only cycle once every 8 to 12 months.
It is generally recommended to spay your dog before her first heat (around 6 months of age) or 2 to 3 months after a heat cycle has completely ended. Spaying during or immediately after a heat cycle carries higher surgical risks due to increased blood flow to the reproductive organs.