Dog Heat Cycle Calculator

November 2023
A dog whose last heat cycle began on 25 Nov 2023 is in the

anestrus stage

TODAY 4 Mar 2024
25 Nov 2023
2 Dec 2023
8 Feb 2024
8 Apr 2024

The heat cycle stages are explained below.

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How do You Use The Dog Heat Cycle Calculator?

Our Dog Heat Cycle Calculator requires the start date of your dog's last heat cycle as input. Once provided, the calculator will estimate the start dates for each stage of your pup's upcoming estrous cycle and visualise them on a timeline. If your dog is currently in a cycle, as indicated by the last heat cycle start date you enter, our calculator will display your dog's current position in the overall cycle timeline.

What is The Dog Heat Cycle?

The dog heat cycle, also known as the estrous cycle, is the reproductive cycle in female dogs that makes them capable of becoming pregnant. Unlike humans, who have a menstrual cycle, dogs have an estrous cycle which is divided into different stages, each characterized by specific hormonal and physiological changes. Understanding these stages is important for dog breeding and health care. The cycle typically occurs about twice a year, but the frequency can vary depending on the breed and individual dog.

Infographic of the dog heat cycle showing details of each stagein the estrus cycle

The table below describes each stage in detail including how long each stage lasts, the characteristc behaviour, hormonal and behavioural changes.

StageDurationCharacteristicsHormonal ChangesBehavioral Changes
Proestrus7-10 days (range: 3-17 days)The beginning stage of the cycle. The female dog starts to exhibit signs such as swelling of the vulva and a bloody vaginal discharge. She begins to attract male dogs but is not yet receptive to mating. Hormonal changes, particularly an increase in estrogen, are prominent.Increase in estrogen levels.Increased interest from male dogs, but the female is not receptive. May show changes in behavior like restlessness or mild aggression.
Estrus5-9 days (range: 3-21 days)The fertile phase of the cycle. The female dog becomes receptive to mating. The vaginal discharge decreases in quantity and becomes lighter in color (straw-colored). Ovulation occurs during this phase, and the dog can become pregnant if mating occurs.Estrogen levels decline and progesterone levels rise.Receptive to male dogs. Exhibits behaviors such as flagging (raising the hindquarters and moving the tail to one side).
Diestrus (or Metestrus)60-90 daysThe phase following estrus. The dog is no longer receptive to males. If the dog has become pregnant, diestrus lasts until she gives birth, which is typically about 63 days. If not pregnant, this stage involves hormonal and physiological decline as the body returns to its normal state.Progesterone levels remain high initially and then decline if the dog is not pregnant.Return to normal behavior. If pregnant, nesting behaviors may be observed.
Anestrus4-5 monthsThe final and longest phase, characterized by inactivity in the reproductive cycle. There is no sexual behavior or hormonal activity. This phase serves as a resting period for the reproductive system and lasts until the beginning of the next proestrus stage.Hormonal activity is at its lowest, the reproductive system is in a resting state.Normal behavior, no interest in mating. Behavior is not influenced by reproductive hormones.

The length and frequency of the heat cycle can vary widely among dogs due to factors like breed, size, age, and individual health. Small breeds may experience more frequent cycles, while larger breeds often have fewer cycles per year. Young dogs may have irregular cycles initially, which usually stabilize as they mature. Understanding these stages is crucial for responsible breeding practices and overall health care of female dogs.

When Do Dogs First Go Into Heat?

Dogs typically experience their first heat cycle, also known as the onset of puberty, between 6 and 24 months of age. However, the exact age can vary significantly based on several factors, including:

  1. Breed: Smaller breeds often come into heat earlier, sometimes as young as 6 months, while larger breeds may take up to 18 months or more. For example, a Chihuahua might reach puberty sooner than a Great Dane.
  2. Individual Differences: Even within the same breed, individual dogs may reach puberty at different ages.
  3. Overall Health and Nutrition: The general health and nutrition of the dog can also influence the timing of the first heat. Well-nourished and healthy dogs are likely to have a more regular onset of puberty.
  4. Environmental Factors: Factors like the presence of other dogs, particularly other females that are in heat, can sometimes influence the timing of a dog's first heat cycle.

Consultation with a veterinarian can provide guidance tailored to an individual dog's health and breed characteristics.

How Do You Care for a Dog in Heat?

Caring for a dog in heat (estrus) requires special attention to both her physical and emotional needs. Here are key points to consider:

  1. Monitor and Manage Bleeding: During the heat cycle, especially in the proestrus and estrus stages, a female dog might have a bloody vaginal discharge. You can use doggie diapers or special pants to keep your home clean. Ensure that these are changed regularly to maintain hygiene.
  2. Prevent Unwanted Mating:
    • Keep your dog on a leash and under close supervision while outside. Dogs in heat can attract male dogs from great distances.
    • Avoid dog parks and areas where male dogs gather.
    • Be vigilant even in fenced yards, as male dogs can be very determined.
  3. Provide a Quiet, Comfortable Space: Dogs in heat may exhibit changes in behavior – they can be more affectionate or, conversely, more irritable. Provide a quiet, comfortable space where your dog can relax away from noise and stress.
  4. Maintain Regular Exercise: While it's important to avoid areas with male dogs, your dog still needs regular exercise. Consider walks during less busy times or play indoors.
  5. Watch for Mood Changes: Your dog may show changes in mood or behavior. She might seem anxious, easily agitated, or more clingy than usual. Be patient and offer extra comfort and attention.
  6. Ensure Good Nutrition and Hydration: Dogs in heat may have changes in appetite. Ensure she has a well-balanced diet and access to fresh water at all times.
  7. Regular Health Checks: Pay attention to any significant changes in her health or behavior. If you notice anything unusual, consult your veterinarian.
  8. Keep a Clean Environment: Regularly clean her bedding and the area where she spends most of her time to prevent infections.
  9. Avoid Stressful Situations: As much as possible, avoid putting your dog in stressful situations. Stress can exacerbate the symptoms of being in heat.
  10. Consider Spaying: If you're not planning to breed your dog, spaying can eliminate the challenges of managing a dog in heat, as well as reduce the risk of certain health problems. Discuss the timing and benefits of spaying with your veterinarian.


  1. Dog estrous cycles: Cornell University College of Veterinary Medicine (July 2023)
  2. Dog - Reproduction, Heat Cycle, Breeding: Britannica