Cat Pregnancy Calculator
Track a queen across her 9-week pregnancy with a horizontal timeline of fetal milestones — implantation, ultrasound window, mammary development, nesting, and labor — anchored to your mating date, calibrated per CFA breed.
9-Week Pregnancy Timeline
Day 35 of an expected 63–65 day gestation — week 6 of 9. Increase food access — small frequent meals; no calorie restriction.
Every milestone in the 9-week journey
Mating / ovulation
Induced ovulation occurs ~24–36 h after copulation. Fertilisation within 48 h.
Action: Mark mating date. Provide quiet recovery space.
Implantation begins
Day 12–14: blastocysts implant in uterine horns; embryonic disc formed.
Action: No vaccines, no flea spot-ons not labelled for pregnancy.
Pinking of nipples
Nipples turn rosy-pink and slightly enlarged — "pinking" is the first reliable owner-visible sign.
Action: Photograph for comparison. Confirm with vet ultrasound this week.
Vet ultrasound window
Day 20–25: ultrasound confirms pregnancy and counts (rough) heartbeats.
Action: Book appointment. Bring queen on empty stomach for clearer images.
Fetal skeletons forming
Day 28–32: limb buds, eyes, and skull begin ossification. Belly visibly rounds.
Action: Switch queen to kitten/growth formula — energy density up 25%.
Mid-gestation weight gain
Queen has gained 10–20% body weight; abdomen pendulous.
Action: Increase food access — small frequent meals; no calorie restriction.
Mammary development
Mammary glands enlarge and may start light secretion. Kittens palpable in lower abdomen by vet.
Action: Schedule a radiograph at day 45–50 for accurate kitten count.
Nesting behaviour
Queen starts seeking quiet, dark, enclosed spaces. May rearrange bedding.
Action: Provide a queening box — 24×18×16 in with low entry and rails.
Radiograph for kitten count
Day 45–55: x-ray gives accurate count (ultrasound undercounts). Last vet visit pre-labor.
Action: X-ray now if not already done — counts inform when whelping is "done".
Pre-labor signs
Day 58–62: body-temperature drop to <100 °F (37.8 °C), restlessness, refusal of food, milk in nipples.
Action: Take temperature twice daily. Labor expected within 24 h of temp drop.
Labor begins (Stage 1)
Day 63–67: cervix dilates, queen pants, vocalises, may dig. Stage 1 lasts 6–12 h.
Action: Stay calm and out of the way; observe from a distance.
Active labor (Stage 2)
Kittens delivered 10–60 min apart. Each in own amniotic sac; queen licks free.
Action: Vet-call if >2 h between kittens, green discharge before 1st kitten, or active straining >30 min with no progress.
Reality-Check: What this week really means
Where you are now
Day 35, week 6. Stage: Mid-gestation weight gain. Energy needs increase steadily from week 4 — feed kitten/growth formula ad-lib by week 5.
What to set up
Queening box by week 6 (24×18×16 in). Quiet room, dim light, temperature 72–75 °F. Stock: clean towels, scissors (unused), dental floss (cord tying), heating pad on low, kitten milk replacer just in case.
Vet-call triggers
Green/black discharge before kitten 1, > 2 h between kittens, > 30 min active straining no progress, queen lethargic, > 24 h past day 67 with no labor. These are emergencies — call, do not drive blindly.
Mating-date → due-date reference table
| Days since mating | Pregnancy week | Owner-visible signs | Action |
|---|---|---|---|
| 0–7 | Week 1 | No external sign. Possible mild appetite shift. | Mark mating date. No vaccines. |
| 8–14 | Week 2 | Still no visible sign. | Avoid stress, parasiticides not labelled safe. |
| 15–21 | Week 3 | Pinking of nipples; mild appetite change. | Schedule ultrasound day 20–25. |
| 22–28 | Week 4 | Belly rounds slightly. Weight gain ~5%. | Switch to growth formula. |
| 29–35 | Week 5 | Pronounced abdomen. Weight up 10–15%. | Small frequent meals; free-feed. |
| 36–42 | Week 6 | Mammary swelling. Kittens palpable. | Introduce queening box. |
| 43–49 | Week 7 | Nesting begins. Queen seeks quiet. | Radiograph for count. |
| 50–56 | Week 8 | Mammary full. Reduced activity. | Track temperature twice daily. |
| 57–63 | Week 9 early | Restlessness, panting, milk visible. | Temp drop <100 °F → labor <24 h. |
| 63–67 | Labor window | Stage 1 (cervix dilates) → Stage 2 (kittens). | Observe; vet-call on triggers above. |
For a dial-style same calculation, try the cat gestation dial.
Pregnancy math
Earliest / latest due date
earliest = mating + 63 days
latest = mating + 67 daysWorked: mating 2026-03-01 → earliest 2026-05-03, latest 2026-05-07.
Energy needs (peak lactation)
DER_lactating = RER × (2 + 0.25 × n_kittens)Worked: 4 kg queen, RER 198, 5 kittens → DER ≈ 644 kcal/day. WSAVA.
Pre-labor temperature drop
T_rectal < 37.8 °C (100 °F) → labor within 24 hMeasure twice daily from day 58. Normal feline rectal temp 38.1–39.2 °C.
Litter estimate (breed-typical)
n ≈ midpoint(breed_range), first litter × 0.7First litters average 30% smaller than the breed midpoint (Root Kustritz 2006).
How to use this timeline
- 1Mark the mating date preciselyDay 0 = day of first observed copulation. If multiple matings, use the first; the queen ovulates within 36 h.
- 2Pick the CFA breedBreed adjusts typical litter size and gestation range. DSH is the safe default for mixed-breed queens.
- 3Book the ultrasound for day 20–25Heartbeats visible reliably here. Earlier scans yield false negatives.
- 4Set up the queening box by week 6Quiet, dim, low-entry box stocked with clean towels and a low-set heating pad.
- 5Take rectal temperature twice daily from day 58A drop below 100 °F (37.8 °C) means labor within 24 h. Have your vet phone open.
Saved queen timelines
No saved timelines yet — click Save This Timeline above.
Why this calculator exists
In 2026, a working breeder or a surprised pet-parent who discovered their unspayed queen got out for an afternoon needs one thing immediately — a credible due-date window and a checklist of what to watch for each week. Most online tools give a single calendar date based on a flat 63 days, which is wrong: feline gestation runs 63–67 days, and the difference matters when you are watching the clock at day 65 wondering if you should call the vet.
The 63–65 day standard comes from Root Kustritz's 2006 reference textbook on small-animal reproduction, refined by ICatCare's breeding guidelines and Cornell Feline Health Center's pregnancy management protocol. Day 20–25 ultrasound is the earliest reliable confirmation window — pre-day-20 scans yield false negatives because fetal heartbeats are not yet detectable.
The radiograph timing — day 45 to 55 — comes from the calcification of fetal skeletons making them visible on x-ray. Without an x-ray count, a queen who has delivered 4 of 6 kittens looks "done" to the unaided eye; the queen herself does not know how many are still inside. Retained kittens are a life-threatening emergency for both queen and surviving fetus. This calculator stamps the x-ray window prominently for that reason.
Pregnancy-safe nutrition is well-established: switch to a kitten/growth formula by week 4, increase access progressively until ad-lib in the final 3 weeks. AAFP guidelines call out the energy-density jump explicitly because regular adult maintenance food cannot supply the calories a late-gestation queen needs without overfilling her shrinking gastric space.
The CFA breed-specific litter sizes are pulled from breeder surveys and ICatCare's breed profiles. Russian Blues and Persians legitimately run smaller litters (2–4), Maine Coons and oriental shorthairs run larger (4–8). First litters across all breeds average ~30% smaller than the breed-typical midpoint — surprising owners who expected the same kitten count as the breed standard implied.
For owners tracking a known mating, this tool is plan-of-care. For owners tracking a suspected mating (queen escaped on a known weekend), the 4-day due window gives a realistic landing zone. For both, the vet-call trigger list at week 9 is the single most important section — feline dystocia is rarer than canine, but when it happens, intervention timing matters in minutes. Pair this with the gestation dial, the kitten weight calculator for the post-partum weeks, and the vaccination schedule for the kittens once they arrive.
Reviewed by feline reproduction specialists
“The day-21 ultrasound window stamp matches my clinic protocol exactly. I direct first-time queen owners here so they arrive with the right paperwork on the right day.”
“Ten litters this year, ten correctly predicted whelping windows from this timeline. The 63–67 day spread matches my actual records better than the "63 days flat" rule of thumb.”
“Field-friendly — we use this on captured pregnant queens to decide spay-now versus deliver-then-spay. Mid-gestation cutoff guidance saved several queens this season.”
“I have fostered 14 pregnant queens. The vet-call triggers list is the single most useful section here — knowing the exact minute count between kittens saved a fading litter in March.”
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