cat calculator
Cat Heat Cycle Calculator: How Long and How Often
Educational estimate, not veterinary advice. These numbers come from published averages and can be wrong for your pet. Your veterinarian, who can examine your dog or cat, is the right person to decide what is healthy for them.
Unlike dogs, cats come into heat again and again during the breeding season until they are mated (or the season ends). Enter the first day of your cat’s last heat to see when it should end and when the next one is likely, based on the reproductive cycle figures in the Merck Veterinary Manual.
A queen’s cycle in numbers
| Feature | Merck Veterinary Manual |
|---|---|
| First heat (puberty) | 4–12 months of age |
| Type of cycle | Seasonally polyestrous: spring through early autumn |
| Length of one cycle | 14–21 days |
| Heat (estrus) | 6–7 days |
| Ovulation | Induced: 24–48 hours after breeding |
| First heat after kittens | 4–6 weeks after giving birth |
| False pregnancy after a sterile mating | about 40 days |
How the calculator counts
If she was not mated:
Heat ends ≈ first day + 5 to 6 days (6–7 days of heat, counting the first day)
Next heat ≈ first day + 14 to 21 days
If she was mated, she may be pregnant: use the cat pregnancy calculator. If the mating doesn’t lead to pregnancy, Merck notes it delays the next cycle by about 45 days, so the 14–21-day count no longer applies.
Worked example
Her heat started on Monday, April 5, 2027, and she was not mated. Heat usually ends: Sat, Apr 10, 2027 – Sun, Apr 11, 2027. Next heat expected: Mon, Apr 19, 2027 – Mon, Apr 26, 2027.
Limitations
- The season matters. Merck describes cats as cycling from spring through early autumn. A cat whose heat ends in late autumn may not cycle again until spring, so the “next heat” date may not come.
- Individual cats vary. Breed, age and the home environment all play a part; her own pattern over a season is the best guide.
- Signs can be subtle in some cats and dramatic in others. If you’re unsure whether she is in heat or unwell, ask your vet.
- Spaying prevents heat cycles and unplanned litters. Your vet can advise on timing.
Frequently asked questions
How long does a cat stay in heat?
The Merck Veterinary Manual's cycle table gives 6–7 days of estrus for queens.
How often do cats go into heat?
Cats are seasonally polyestrous: during the breeding season, spring through early autumn, an unmated queen comes back into heat every 14–21 days (Merck).
How old are cats at their first heat?
Merck gives puberty at 4–12 months.
Can a cat go into heat right after having kittens?
Yes. Merck's table gives the first heat after giving birth at 4–6 weeks.
Do cats ovulate on their own?
Usually not. Cats are induced ovulators: Merck notes ovulation occurs 24–48 hours after breeding. A mating that doesn't lead to pregnancy can cause a false pregnancy of about 40 days and delay the next cycle by about 45 days.
Sources
- Merck Veterinary Manual. Features of the Reproductive Cycle (table). Checked October 25, 2026.
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