Canine Heat Cycle Calculator
Enter the start date of your dog's last heat cycle to see a complete timeline of stages, fertile window, optimal breeding days, and expected whelping dates.
How This Is Calculated
This calculator uses average durations from veterinary reproductive science. A typical canine estrous cycle lasts approximately 180 days (6 months) and consists of four stages:
| Stage | Duration | Description |
|---|---|---|
| Proestrus | ~9 days | Bleeding begins, vulva swells, males attracted but female not receptive |
| Estrus | ~9 days | Fertile window — female receptive, ovulation occurs |
| Diestrus | ~60 days | Pregnancy (if bred) or return to non-receptive state |
| Anestrus | ~102 days | Rest phase — reproductive system recovers |
Formula
- Fertile Window = Start Date + 9 days (beginning of estrus) through Start Date + 17 days (end of estrus)
- Optimal Breeding = Days 10–13 from start (2–5 days into estrus, after ovulation)
- Expected Whelping = Optimal breeding date + 58–68 days (average canine gestation)
- Next Heat Cycle = Start Date + 180 days
How to Use
- Enter the first day you noticed signs of heat (bleeding, vulvar swelling) in the date field above.
- Results appear instantly — no button needed.
- Review the visual timeline to see where your dog is in the cycle.
- Check the Key Dates section for the fertile window, optimal breeding days, and whelping estimate.
- Use the Print button to save a copy for your veterinarian.
Disclaimer: These calculations are based on average values. Individual dogs vary — cycle length can range from 4 to 13 months depending on breed, age, and health. Small breeds tend to cycle more frequently; giant breeds less so. Always consult a licensed veterinarian for breeding decisions and health concerns.
