Dog Heat Cycle Calculator
Tracking your dog's heat cycle helps with breeding plans or avoiding unwanted pregnancies. Enter the date her last heat started and her typical cycle length to see the estimated phases, fertile window, and when to expect the next heat.
The canine estrous cycle has four stages:
1. Proestrus (days 1-9): The beginning of heat. The vulva swells and there is a bloody vaginal discharge. The female attracts males but is not yet willing to breed. This phase lasts about 7-10 days.
2. Estrus (days 9-14): The fertile period. Discharge lightens in color (straw-colored), and the female becomes receptive to mating. Ovulation typically occurs about 2 days after the LH surge, usually around days 10-12. Eggs take another 2-3 days to mature after ovulation. This is the optimal breeding window.
3. Diestrus (days 14-70+): The female is no longer receptive. If pregnant, this phase lasts through the 63-day gestation. If not pregnant, the body goes through a "pseudopregnancy" phase that lasts about 60 days.
4. Anestrus (variable): The quiet resting phase between cycles. Length varies by breed and individual.
Cycle frequency by breed size:
- Small breeds (Chihuahua, Yorkie): every 4-6 months
- Medium breeds (Beagle, Cocker Spaniel): every 6-7 months
- Large breeds (Lab, Golden Retriever): every 6-8 months
- Giant breeds (Great Dane, Saint Bernard): every 8-12 months
Some breeds like Basenjis and Tibetan Mastiffs only cycle once per year. Individual dogs vary, so tracking over 2-3 cycles gives you the most accurate prediction.
For precise breeding timing, veterinarians can measure progesterone levels via blood tests. This is especially helpful for artificial insemination or when using shipped semen.