Guinea pigs carry their young for about two months, which is long for a small animal. The pups are born well developed, with fur and open eyes.
Enter the date she was with the boar to see the likely birth window.
How to use the Guinea Pig Pregnancy Calculator#
- Enter the breeding date. Use the date of mating, or of insemination.
- Check the length. Leave the average, or enter your vet’s figure for the breed.
- Read your dates. You get the expected date, the likely window and your guinea pig’s progress.
How long is a guinea pig pregnant?#
Gestation runs from about 59 to 72 days, with an average of around 65. Larger litters tend to arrive a little earlier.
| Days | |
|---|---|
| Average | 65 |
| Usual range | 59 to 72 |
Getting ready for the pups#
Pregnant sows need extra vitamin C, good hay and fresh water, and a roomy, quiet home. A vet who knows guinea pigs can check her health and advise on diet. First-time sows that are older than about seven or eight months can have problems at birth, so ask your vet before breeding.
Pups can start eating solids within days and the boar and sow need separating from the young before they mature, to prevent more pregnancies. Call a vet if she seems unwell, stops eating, or has trouble giving birth.
Why the date is a window#
The range for a guinea pig is wide, 59 to 72 days, with an average of around 65. Larger litters tend to arrive earlier, so a sow carrying several pups may sit at the early end while one carrying a single pup is more likely to go longer. This calculator is a planning tool and doesn’t replace veterinary advice.
A worked example#
A sow was paired with a boar on Mon 3 May 2027. At 65 days the pups are due on Wed 7 July 2027. The window is wide, from Thu 1 July 2027 to Wed 14 July 2027, because guinea pigs differ a lot from one animal to the next. Smaller litters are carried longer and larger litters come sooner, so a sow expecting one pup can pass day 70 without anything being wrong.
| Milestone | Day | Date |
|---|---|---|
| Halfway | 33 | Sat 5 June 2027 |
| Final stretch begins | 55 | Sun 27 June 2027 |
| Earliest likely birth | 59 | Thu 1 July 2027 |
| Expected due date | 65 | Wed 7 July 2027 |
| Latest likely birth | 72 | Wed 14 July 2027 |
Two timing rules that matter more than the date#
First, a sow’s pelvis fuses if she is not bred before about seven or eight months old. A first pregnancy after that point can lead to a blocked birth that needs an emergency caesarean. Many vets advise against breeding a sow for the first time once she is over about six months.
Second, a sow can become pregnant again within hours of giving birth. If the boar is still in the cage on birth day, she can be carrying a second litter before the first is weaned. Separate him on the due date in the window, not afterwards, and keep them apart.
What to watch for in the final weeks#
Weigh her once a week from the start. A steady gain is normal, and from about the fifth week the pups can be felt moving. Offer plenty of hay, fresh vegetables rich in vitamin C and unlimited water, as sows cannot make their own vitamin C and need more of it when pregnant.
Pregnancy toxaemia is the main danger, especially in overweight sows. Refusing food, sitting hunched, and breathing that smells sweet are signs to take her to an exotics vet at once. In the last few days a vet can feel the pubic bones loosening, which is a good sign that birth is close.
Pups arrive furred, with eyes open, and begin nibbling hay within a day or two. Keep the cage quiet, with a low shelter and no tall drops, from the final-stretch date of Sun 27 June 2027 onward.
Preparing the cage before the window opens#
By day 55 or so, clear out anything the pups could fall from or get stuck under: tall platforms, wheels, gaps in ramps. Use plain paper or fleece bedding with no fine dust, and put in a low hideout big enough for the sow and several pups. Keep a record of when you separated the boar, because the calculator is only useful if the starting date is right.
When a late date is not a worry#
A sow that goes past day 65 is common, especially with a small litter. What matters is her behaviour. If she is eating, moving about and her weight is steady, give her time. If she stops eating, seems in pain, or you see blood or discharge with no pup, take her to the vet the same day.
Frequently asked questions#
About 65 days, with a range of roughly 59 to 72 days.
Often two to four, but litters vary.
They nurse for a few weeks, but eat solid food very early.
Ask your vet. It’s usually done at a few weeks, before they mature.