Free biology calculators for genetics, cells, pregnancy timelines, and life sciences. Backed by reference data.
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Biology calculators take the routine arithmetic and date math out of common life-sciences problems. The cat pregnancy calculator, for instance, uses the Cornell Feline Health Center's reference gestation length (63–67 days from breeding) and lays out the major milestones — implantation, palpation window, nesting, and likely birth date — so you don't have to count on a calendar.
These calculators are reference tools built on published veterinary and biomedical data, but they're not a substitute for a vet visit. Cats, like humans, can vary from the textbook gestation length, and any sign of complications (lethargy, bleeding, missed milestones) should send you to a vet, not a website. Use the timelines as a planning aid alongside professional care.
Feline gestation typically lasts 63 to 67 days from the date of conception, with 65 days being the most common length. Some cats deliver as early as 60 days or as late as 70, both of which are still within normal range. Litters delivered before day 60 are usually premature; pregnancies extending past day 70 warrant a vet check. The cat pregnancy calculator lets you enter the breeding date and see all three estimates (early, expected, late).
How can you tell if a cat is pregnant?
Early signs (weeks 2–3): "pinking" of the nipples, mild appetite changes, and increased affection. A vet can confirm pregnancy by palpation around day 17–25, or by ultrasound from around day 20. Mid-pregnancy (week 5+): noticeable belly rounding and weight gain. Late pregnancy (week 7+): visible kitten movement on the belly walls. X-ray is the most reliable late-stage method and also reveals the kitten count.
When can you feel kittens move in a pregnant cat?
You can usually feel fetal movement from around day 50 (week 7) onward, when kittens are large enough to move against the abdominal wall. Gentle palpation of the lower belly will sometimes reveal movement, though don't press hard — fetal palpation should be left to the vet. By week 8, movement is often visible from the outside, particularly when the queen is resting.
What signs indicate a cat is about to give birth?
Within 24–48 hours of birth: nesting behavior (seeking out hidden spots), restlessness, loss of appetite, and a drop in rectal temperature from about 38.6°C (101.5°F) to under 37.8°C (100°F). Some queens vocalize more or become unusually clingy. Once active labor starts, you'll see visible contractions; the first kitten should appear within an hour. If contractions go beyond an hour without delivery, call a vet.