Mouse Gestation Calculator
Last updated
A mouse's gestation period is about 20 days, or roughly 0 months and 2 weeks, though it ranges from 19 to 21 days depending on breed and individual animal.
Calculate a pup due date
Estimated birthing date
Monday, 16 November 2026
Earliest
15 Nov 2026
Latest
17 Nov 2026
0 of 20 days elapsed
Milestone timeline
| Day | Milestone | Date |
|---|---|---|
| 1 | Separate the male — a doe can conceive again within a day of birth | 28 Oct 2026 |
| 8 | Weight gain becomes detectable on a small digital scale | 4 Nov 2026 |
| 12 | Belly becomes obviously pear-shaped; increase protein | 8 Nov 2026 |
| 16 | Final cage clean and extra nesting material | 12 Nov 2026 |
| 19 | Earliest normal birth — do not disturb the nest | 15 Nov 2026 |
| 20 | Expected birth | 16 Nov 2026 |
| 28 | Separate the litter by sex before they can breed | 24 Nov 2026 |
How to use the mouse gestation calculator
- 1. Choose what you know. Enter the breeding date to get a due date, or switch to the target due date mode to work backwards to the breeding date you need.
- 2. Refine the inputs. The calculator uses the 20-day average for this species.
- 3. Plan around the range. Use the earliest and latest dates and the milestone timeline to schedule checks, feed changes and preparation of the birthing area.
How long is a mouse's gestation period?
The average is 20 days from breeding to birthing, about 0 months and 2 weeks. Anything between 19 and 21 days is normal, and a typical litter is 5-8 pups. Treat the calculated date as the middle of that window rather than a fixed appointment.
Mouse gestation table: breeding date to birthing date
Breeding dates one week apart with the matching birthing date at 20 days.
| Breeding date | Expected birthing date |
|---|---|
| 27 Oct 2026 | 16 Nov 2026 |
| 3 Nov 2026 | 23 Nov 2026 |
| 10 Nov 2026 | 30 Nov 2026 |
| 17 Nov 2026 | 7 Dec 2026 |
| 24 Nov 2026 | 14 Dec 2026 |
| 1 Dec 2026 | 21 Dec 2026 |
| 8 Dec 2026 | 28 Dec 2026 |
| 15 Dec 2026 | 4 Jan 2027 |
| 22 Dec 2026 | 11 Jan 2027 |
| 29 Dec 2026 | 18 Jan 2027 |
| 5 Jan 2027 | 25 Jan 2027 |
| 12 Jan 2027 | 1 Feb 2027 |
Working backwards from a target birthing date
If you want pups on the ground in a particular week, switch the calculator to target date mode and enter the date you are aiming for. It subtracts 20 days to give the breeding date to book, plus the earliest and latest service dates that still land inside your window.