Enter the first mating date and the due window and timeline dates will appear here.
Breeding timeline
- D21
Palpation window
An experienced hand can feel a string of grape-sized swellings in the abdomen. This is the only window: earlier there is nothing to feel, and later the uterine contents merge into one mass and individual kittens can no longer be told apart. Heavy handling can cause resorption or miscarriage — if you are not confident, leave it to your vet.
- D25–30
Ultrasound to confirm pregnancy
Foetal heartbeats are clearly visible by now, making this the most reliable way to confirm both pregnancy and viability. Ultrasound answers "is she pregnant" and "are they alive", but it cannot count reliably — kittens hide behind one another.
- D45
X-ray for litter count
Foetal skeletons have calcified, so an X-ray can now count skulls. Knowing the exact number is what makes the delivery safe: a queen who has one kitten left inside and nobody counting is the standard route to a retained foetus, infection and death.
- D55
Set up the nesting box
Put the box in a quiet, dim, temperature-stable room and let her get used to it a week ahead, or she will pick a wardrobe when the time comes. Disinfect the whelping area and have clean towels, a bulb syringe, dental floss for tying cords, a gram scale and a heat pad ready.
- D57
Start twice-daily temperature checks
Take and log a rectal temperature morning and evening. A drop below 99°F (37.2°C) usually means labour within 24 hours — the single most reliable sign in the whole pregnancy, more dependable than any change in behaviour.
- D63–65
Due window
Most normal deliveries happen in this range. Call the vet immediately if nothing has happened by D67, if hard straining goes past 30 minutes with no kitten, or if more than 2 hours pass between kittens.
Why the due date is a window, not a day
Cats are induced ovulators: eggs are not released on a cycle but in response to mating, usually 24–48 hours afterwards, and it often takes several matings to trigger a full release. So there is always a day or two of drift between the mating date and the conception date, and more when she mated repeatedly. An honest calculator therefore does not name a single day — it brackets everything from first mating + 63 to last mating + 65. A window that is slightly wide costs you a few days of early preparation; false precision costs you the delivery.
Which checkpoints cannot be skipped
The D25–30 ultrasound and the post-D45 X-ray answer completely different questions and neither replaces the other: ultrasound confirms that she is pregnant and the kittens are alive, the X-ray establishes how many there are. A great many breeding disasters start with a skipped X-ray — labour appears to finish, nobody knows one is still inside, and the uterine infection that follows can kill within days. Temperature monitoring from D57 is equally load-bearing: it is the only quantifiable warning you get, and a rectal temperature below 99°F (37.2°C) usually means labour starts within 24 hours.
When to go to the vet immediately
Do not wait if any of these appear: hard straining for 30 minutes with no kitten produced; more than 2 hours between kittens while she is still straining; two days past the end of the due window (D67) with no sign of labour; foul-smelling or dark green discharge before any kitten has been born; or a temperature above 103°F (39.5°C) combined with marked lethargy. Taping the number of the nearest clinic that performs emergency caesareans to the whelping-room wall matters more than any other preparation in the pregnancy.
Frequently asked questions
How long are cats pregnant?
Feline gestation runs 63–65 days, with a normal range extending to about 67. The reason a calculator gives a window rather than a date is that mating is not conception: cats are induced ovulators, ovulation follows mating by roughly 24–48 hours, and repeated matings make the actual conception day harder still to pin down. This tool therefore runs from first mating + 63 days to last mating + 65 days, covering every plausible date.
How early can you confirm a cat is pregnant?
In order of reliability: palpation around D21, where an experienced hand feels a string of swellings — effective but risky if done heavily; ultrasound at D25–30, which shows foetal heartbeats and is the most reliable confirmation of a live pregnancy, though it cannot count accurately; and X-ray after D45, once skeletons have calcified and skulls can be counted. They are not substitutes for each other — ultrasound answers whether, X-ray answers how many.
Do I really need an X-ray to count the kittens?
Yes, because you need to know when she has finished. If the X-ray showed five and only four have been delivered, the retained kitten causes infection, possible uterine rupture and can kill the queen — and nothing about her appearance will tell you. Counting by X-ray after D45 is the highest-value scan of the whole pregnancy: it is inexpensive, and it is the only objective basis for deciding that labour is over.
What are the signs a cat is about to give birth?
Temperature is the most reliable one. From D57, take a rectal temperature twice daily; normal is 100.5–102.5°F (38–39°C), and a drop below 99°F (37.2°C) usually means labour within 24 hours. Behaviourally you will see refusing food, going in and out of the nesting box, nesting behaviour, restlessness and clinginess, and increased vulval discharge. The temperature method beats every behavioural sign, which is why D57 gets its own entry on this timeline.
She mated several times — which date do I use?
Enter both. Put the first mating in the required field and the last one in the optional field, and the window is calculated as first + 63 through last + 65. Because cats are induced ovulators, ovulation may have followed any of the matings, so a window built from both ends is honest where a single date would be false precision.