Dog Heat Cycle Calculator

Predict your dog's next estrus period.

Prediction:

Understanding the Canine Estrus Cycle

Unlike humans who have a monthly cycle, dogs typically go into "heat" (estrus) once or twice a year. Knowing when to expect this cycle is crucial for preventing unwanted litters, planning for puppies, or simply managing the behavioral changes that come with it.

The 4 Stages of the Heat Cycle

The reproductive cycle consists of four distinct phases, though typically owners only notice the first two:

1. Proestrus (Start of "Heat")

Duration: 9 days average (ranges 0-17 days)

Signs: Swelling of the vulva and bloody discharge. Males are attracted to the female, but she will refuse to mate, often tucking her tail or snapping at them.

2. Estrus (Mating Period)

Duration: 9 days average (ranges 3-21 days)

Signs: Discharge changes color to straw-yellow or pink. The vulva remains swollen but softer. This is the fertile window. The female will accept the male and may "flag" (move her tail to the side).

3. Diestrus

Duration: Approx. 60 days

Signs: The fertile period ends. Hormonally, this stage mimics pregnancy even if the dog is not pregnant. Some dogs may experience a "false pregnancy" with nesting behavior or milk production during this time.

4. Anestrus

Duration: 4-5 months (varies by breed)

Signs: The "resting" phase. There are no hormonal or behavioral signs. The body is preparing for the next cycle.

How Often Do Dogs Go Into Heat?

The average is every 6 months, but this varies significantly by size and breed:

Small Dogs: May cycle 3-4 times a year (every 4 months).
Large/Giant Dogs: Often cycle only once every 9-12 months.
Basenjis & Primitive Breeds: Typically only cycle once a year, usually in the fall.

Management Tips

During the 2-3 week heat period, keep your dog on a leash at all times outside. Male dogs can smell a female in heat from miles away and may jump fences to get to her. If you do not plan to breed, consider spaying your dog to eliminate these cycles and reduce the risk of mammary cancer and uterine infections (Pyometra).