Dog Heat Cycle Calculator
Predict your dog's next heat cycle, fertile window and whelping date — by breed size
📅 Dog Heat Cycle Calculator
Predict next heat, fertile window, and whelping date based on last cycle
How Long is a Dog’s Heat Cycle?
The average interval between heat cycles is 6 months for most breeds, but this varies considerably. Small breeds may cycle every 5 months. Giant breeds like Great Danes and Saint Bernards often cycle only once a year or every 18 months.
Signs of Heat
The first signs are a swollen vulva and bloody discharge — this is the proestrus stage. After about 9 days, discharge lightens and the female becomes receptive to mating — this is estrus, the fertile window. The entire visible heat lasts around 2–3 weeks.
When Is a Dog Most Fertile?
Peak fertility occurs approximately 10–14 days after the first signs of heat, during the estrus stage. However, the only reliable way to confirm ovulation timing is progesterone testing at a veterinary clinic — essential for planned breedings.
Preventing Unwanted Pregnancy
Keep intact females strictly separated from intact males during and immediately after the heat cycle. Males can smell a female in heat from significant distances. A female can become pregnant even at the very beginning or end of her cycle.