Cat Pregnancy Calculator (kitten due date & stages)

Understanding the cat pregnancy calculator — concept and principle

This calculator estimates when a pregnant cat (queen) will give birth from the date of mating, and shows where she is in the pregnancy today. Breeders and owners use it to prepare a nesting box, book a vet check and know when to watch closely for labour.

How it is calculated

All dates are counted from the mating date:

• Most likely birth = mating + 65 days; typical window = day 64 to day 66.
• Earliest normal birth = day 60.
• A vet can usually detect pregnancy from day 21; an X-ray can count kittens after day 55.
• Days since mating = today − mating date; week of pregnancy = floor(days ÷ 7) + 1, shown up to day 70.
• The stage is chosen from the day count: under 21 too early to confirm, 21–30 detectable, 31–54 kittens developing, 55–59 X-ray can count, 60–66 birth can happen any day, after 66 call your vet.

The principle

A cat's pregnancy lasts about 60–65 days from conception, and most kittens arrive 64–66 days after mating. Cats ovulate in response to mating, but mating can happen on several days and conception may follow it, so the true start is uncertain by a day or two. Counting from mating is still the most practical anchor. The milestones match how a pregnancy can be checked: by about day 21–30 a vet can feel the small swellings in the uterus or see them on ultrasound, and from about day 55 the kittens' skeletons contain enough mineral to show on an X-ray.

Worked example

Default inputs: mating on Oct 11, 2026, viewed on Nov 10, 2026.

1. Day 65: Oct 11 + 65 days = Tue, Dec 15, 2026; window Dec 14 to Dec 16.
2. Earliest normal birth, day 60 = Thu, Dec 10, 2026.
3. Days since mating = 30; week = floor(30 ÷ 7) + 1 = 5.
4. Day 30 falls in 21–30, so the stage is a vet can usually detect it (from Sun, Nov 1).
5. X-ray kitten count after day 55 = Sat, Dec 5, 2026.

How to read the result

Treat the birth date as the middle of a window, not an appointment. From about day 60, keep the queen indoors and offer a quiet, warm box. Restlessness, hiding, nesting and loss of appetite often show labour is near. The stage line updates every day, so open the page again as the date approaches.

Common mistakes

• Using the first day of heat rather than the mating date.
• Expecting the birth exactly on day 65.
• Assuming the pregnancy is confirmed before a vet has checked.
• Forgetting that more than one mating date shifts the window.

Frequently asked questions

How long is a cat pregnant?

About 60–65 days from conception; kittens are usually born 64–66 days after mating.

When can a vet confirm pregnancy?

Usually from about day 21–30, by gently feeling the belly or by ultrasound.

When can I find out how many kittens there are?

An X-ray after about day 55 can count them because the skeletons are visible by then.

Sources: Merck Veterinary Manual (pet owner version), "Management of Reproduction of Cats"