Rat Gestation Calculator

Fancy rats carry their litters for roughly 21 to 23 days, so a due date arrives fast. Enter the pairing or exposure date above for a due window, then set up a calm, secure nesting cage using the notes below. For health questions, consult your veterinarian.

Rat gestation at a glance

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

• Average length: 22 days
• Typical range: 21 to 23 days
• Litter size: 6 to 12 kittens
• Large litters: up to 15
• Pups born: hairless and blind
• Fur appears: about 1 week
• Eyes open: 14 to 17 days
• Weaning age: about 21 days
• Postpartum heat: within 24 hours
• Female name: doe
• Male name: buck
• Baby name: kitten or pup

Newborn rat milestones

Baby rats, called kittens, are helpless at birth and grow quickly.

• Day 1: pink and blind
• Day 4: skin pigment shows
• Day 6: fuzz appears
• Day 8: full fur
• Day 10: ears open
• Day 15: eyes open
• Day 16: exploring
• Day 18: eating solids
• Day 21: weaning
• Week 4: separate by sex
• Week 5: sexual maturity
• Week 6: independent

Frequently asked questions

How long are rats pregnant?

Rat gestation averages about 22 days and usually ranges from 21 to 23 days. A doe nursing a previous litter can carry a touch longer. Because the pregnancy is short, does often show an obvious pear shape only in the last three or four days before delivering.

Can a rat get pregnant right after giving birth?

Yes. Does enter a fertile postpartum heat within roughly 24 hours of birth, so a buck left in the cage can breed the doe again straight away. Removing the male before the litter arrives is the standard way to prevent an immediate, draining second pregnancy.

How many babies do rats have?

Litters typically run 6 to 12 kittens, and large litters can reach 15 or more. Very big litters may leave some kittens underfed, so check that each has a visible milk band in the belly during the first days and ask your veterinarian if any pup looks left behind.

When do baby rats open their eyes?

Kittens are born hairless and blind, grow a full coat by about a week, and open their eyes between 14 and 17 days. They begin tasting solid food soon after and are generally weaned by three weeks, when males and females should be separated to avoid early litters.