Guinea pigs are pregnant for about 59 to 72 days, averaging roughly 68 days — around 9 to 10 weeks (Merck Veterinary Manual). Enter the date your sow was bred into the calculator above and it returns her estimated due date, the earliest and latest likely birth dates, and a week-by-week care timeline.
The number the calculator uses
The tool adds 68 days to the breeding date for the estimated due date and shows a full birth window of 59–72 days. The Merck Veterinary Manual gives a range of 58–72 days from breeding, narrowing to 62–64 days when timed from ovulation. Veterinary sources such as Harlingen Veterinary Clinic cite a typical average of 63–68 days. One reliable pattern: the larger the litter, the shorter the pregnancy tends to be, so big litters often arrive nearer the early end of the window.
How long are guinea pigs pregnant?
A guinea pig’s pregnancy length runs from about 59 to 72 days, with most sows giving birth around day 63–68. This is long for a rodent, and it’s why guinea pig pups are born “precocial” — fully furred, eyes open, and able to nibble solids within a day. Because gestation is measured from the day she was housed with a boar (the exact mating time is rarely known), treat the due date as a window rather than a fixed day. If your guinea pig stays pregnant past day 72 without giving birth, contact an exotics vet.
Do guinea pigs have periods?
No. Guinea pigs do not menstruate and should not bleed. Instead of shedding the uterine lining like humans, a sow reabsorbs it, so there is no visible period (A-Z Animals). What they have is an estrous cycle of about 16 days (peer-reviewed studies put it at 14–17 days), during which the sow is fertile for only around 6–11 hours, usually at night. Any bleeding from the genitals is not a normal “period” and warrants a prompt vet visit.
Guinea pig gestation reference chart
| Measure | Days from breeding | Notes |
|---|---|---|
| Earliest birth | ~59 days | Larger litters tend to arrive first |
| Typical average | 63–68 days | Roughly 9–10 weeks |
| Calculator estimate | 68 days | Used for the due date shown above |
| Latest expected | 72 days | Call a vet if she hasn’t delivered |
| From ovulation | 62–64 days | Per the Merck Veterinary Manual |
| Litter size | — | 1–8 pups, typically 2–4 |
How to use the guinea pig gestation calculator
- Enter the breeding or mating date — or the day she was last housed with an intact male if you’re unsure.
- Read the estimated due date (breeding date + 68 days) at the top of the result panel.
- Note the earliest (day 59) and latest (day 72) dates — this is her realistic birth window.
- Follow the care timeline for vet confirmation, separating the boar, and watching for complications.
- Use Print / save to keep a copy for your records.
BarnCalc · Guinea Pigs
Guinea Pig Gestation Calculator
Enter the breeding date to estimate your cavy's due date and birth window.
If you don't know the exact date, use the day she was last housed with a boar.
Estimated due date (avg 68 days)
—
Enter a breeding date above.
Care & management timeline
Guinea pig gestation reference chart
| Measure | Days from breeding | Notes |
|---|---|---|
| Earliest birth | ~59 | Larger litters often arrive first |
| Typical average | 63–68 | ~9–10 weeks |
| Calculator estimate | 68 | Used for the due date above |
| Latest expected | 72 | Call your vet if no birth by now |
| From ovulation | 62–64 | Merck Vet Manual |
Litter size 1–8 pups (typically 2–4). Estrous cycle ~16 days — guinea pigs do not have periods or bleed.
Frequently asked questions
How do you know if a guinea pig is pregnant?
Early on it’s hard to tell. The clearest home sign is steady weight gain and a firm, enlarging, pear-shaped abdomen from about week 3. A vet can confirm pregnancy by gentle palpation — reliable between roughly day 15 and day 30 with about 98% accuracy in one study (PubMed) — or by ultrasound.
How long do guinea pigs stay pregnant?
About 59–72 days, most often 63–68 days. Larger litters usually mean a slightly shorter pregnancy.
How many babies do guinea pigs have?
Litters range from 1 to 8 pups, with 2–4 being most common. Pups are born fully developed and can eat solids within a day, though they still nurse.
Can a guinea pig get pregnant right after giving birth?
Yes. Sows enter a fertile postpartum estrus within about 15 hours of giving birth, so the boar must be removed before delivery to prevent back-to-back pregnancies.
Is it safe to breed my guinea pig?
Breeding carries serious risks, including pregnancy toxemia and dystocia. A sow bred for the first time after about 7 months is prone to a stiffened pubic symphysis that can block delivery (PetMD). Always plan breeding with an exotics vet.
How can I tell birth is near?
In the last day or two the pubic bones separate under the hormone relaxin — a vet can often feel a gap of about 15 mm roughly 48 hours before birth. Restlessness may appear, but guinea pigs build little or no nest.
Sources
- Merck Veterinary Manual — Approximate Gestation Periods: merckvetmanual.com
- PetMD — Difficulty Giving Birth (Dystocia) in Guinea Pigs: petmd.com
- PubMed — Pregnancy diagnosis in the guinea pig (palpation): pubmed.ncbi.nlm.nih.gov
- Harlingen Veterinary Clinic — How Long Are Guinea Pigs Pregnant: harlingenveterinaryclinic.com
- A-Z Animals — Do Female Guinea Pigs Have Periods: a-z-animals.com
- Hepper (vet-approved) — Guinea Pig Pregnancy: articles.hepper.com
Reviewed for accuracy against the Merck Veterinary Manual, PetMD, PubMed, and Harlingen Veterinary Clinic.
Last updated: July 16, 2026.