Mouse Gestation Calculator

Mice have one of the shortest pregnancies you will track, usually 19 to 21 days. Enter the pairing or exposure date above for a due window, then use the facts below to prepare a quiet nesting setup. For any health concern, consult your veterinarian.

Mouse gestation at a glance

Typical averages for pet and fancy mice; individual does vary.

• Average length: 20 days
• Typical range: 19 to 21 days
• Litter size: 5 to 12 pups
• Pups born: hairless and blind
• Fur appears: about 1 week
• Eyes open: about 13 days
• Weaning age: about 21 days
• Postpartum heat: within 24 hours
• Female name: doe
• Male name: buck
• Baby name: pinkie or pup
• Sexual maturity: 6 to 8 weeks

Newborn mouse milestones

Pups are altricial, meaning helpless at birth, and develop fast.

• Day 1: pink and blind
• Day 3: skin darkens
• Day 4: fuzz begins
• Day 7: fur coat
• Day 10: ears open
• Day 13: eyes open
• Day 14: exploring nest
• Day 16: eating solids
• Day 21: weaning
• Week 4: separate by sex
• Week 6: sexual maturity
• Week 8: fully grown

Frequently asked questions

How long are mice pregnant?

Mouse gestation averages about 20 days and typically ranges from 19 to 21 days. Nursing a large litter can stretch it slightly. Because the window is so short, it is easy to miss a pregnancy until the doe visibly rounds out in the final few days.

Can a mouse get pregnant right after giving birth?

Yes. Does come into a fertile postpartum heat within about 24 hours of delivering, so a male left in the enclosure can breed the doe again immediately. Separating the buck before the birth is the usual way to avoid back to back litters that exhaust the mother.

How many pups are in a mouse litter?

Litters commonly run 5 to 12 pups, and first time or young does often have fewer. Very large litters can leave some pups underfed, so watch that every pup has a round milk filled belly in the first days and ask your vet if any are being left behind.

When do baby mice open their eyes?

Pups are born hairless and blind, grow a full fur coat by about a week, and open their eyes around day 13. They start sampling solid food soon after and are usually weaned by three weeks, at which point males and females should be separated to prevent early breeding.