Heat cycle calculator: when will my dog's or cat's next heat be?
Enter the species and the start date of the last heat cycle to estimate when the next heat should begin and the approximate fertile window of this cycle.
Dogs typically go into heat about 2 times a year (roughly every ~6 months).
Enter the start date of the last heat cycle to see the result.
Every pet is different
Intervals between heat cycles vary individually, and this calculator is only an educational estimate. Spaying is a safe and effective way to prevent heat cycles, unwanted pregnancies, and to reduce health risks such as pyometra and mammary tumors — talk to a veterinarian about the best timing for your pet.How the calculation works
Dogs are monoestrous: they typically go into heat about 2 times a year, with an average interval of 6 months between one heat and the next. Within each cycle, the window of highest fertility usually occurs between days 9 and 14 after the start of heat.
Cats are seasonally polyestrous: during the breeding season, if not bred, heat tends to repeat every 2 to 3 weeks (we use an average of 18 days). Unlike dogs, cats tend to remain receptive and fertile for nearly the entire estrus period.
These are averages based on veterinary literature — the actual interval varies from animal to animal, depending on age, breed, overall health, and, in cats, exposure to natural light. Use the result as a reference and watch for your pet's physical and behavioral signs.
Frequently asked questions
What are the signs that my dog or cat is in heat?
In dogs, the most common signs are a swollen vulva, bleeding (proestrus), frequent licking of the genital area, behavior changes, and attracting males. In cats, heat usually shows up as intense vocalization (loud meowing), restlessness, a lordosis posture (raising the hindquarters), and increased need for attention — usually without visible bleeding.
Why does spaying reduce health risks?
Spaying eliminates the risk of pyometra (a serious uterine infection) and significantly reduces the risk of mammary tumors, especially when done before the second or third heat. It also prevents unwanted pregnancies and some heat-related behaviors. The decision about when to spay should be discussed with a veterinarian, taking into account the age, size, and health of the animal.
What's the difference between a dog's heat and a cat's heat?
Dogs are monoestrous: they have about 2 heat cycles a year, with an average interval of 6 months between them, regardless of season. Cats are seasonally polyestrous: during the breeding season (which can last all year for indoor cats exposed to artificial light), heat can repeat every 2 to 3 weeks if the cat is not bred.
What is a false pregnancy (pseudocyesis)?
It is a common condition in dogs (rarer in cats) in which, after heat, the body shows signs of pregnancy — such as enlarged mammary glands, milk production, and "nesting" behavior with objects — even without fertilization. It is usually caused by natural hormonal fluctuations after heat and often resolves on its own, but persistent or uncomfortable cases should be evaluated by a veterinarian.
Can I fully rely on the predicted date of the next heat cycle?
No — it is only an estimate based on species averages. The interval between heat cycles varies from animal to animal and can be influenced by age, breed, overall health, and, in cats, exposure to natural light. Use the prediction as a reference and watch for physical and behavioral signs to confirm the start of heat.
Important notice
This calculator is for educational purposes and does not replace a veterinary evaluation. When in doubt, consult a veterinarian.Sources
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