Grizzly Bear Gestation Calculator
Last updated
A grizzly bear's gestation period is about 235 days, or roughly 7 months and 3 weeks, though it ranges from 180 to 250 days depending on breed and individual animal.
Calculate a cub due date
Estimated birthing date
Friday, 28 May 2027
Earliest
3 Apr 2027
Latest
12 Jun 2027
0 of 235 days elapsed
Milestone timeline
| Day | Milestone | Date |
|---|---|---|
| 0 | Mating in late spring or early summer | 5 Oct 2026 |
| 150 | Delayed implantation ends in late autumn, around when the female enters her den | 4 Mar 2027 |
| 210 | Cubs develop rapidly during the short period of active growth | 3 May 2027 |
| 235 | Expected birth in the den in mid winter | 28 May 2027 |
How to use the grizzly bear 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 235-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 grizzly bear's gestation period?
The average is 235 days from breeding to birthing, about 7 months and 3 weeks. Anything between 180 and 250 days is normal, and a typical litter is 1-3 cubs. Treat the calculated date as the middle of that window rather than a fixed appointment.
Grizzly bear gestation table: breeding date to birthing date
Breeding dates one week apart with the matching birthing date at 235 days.
| Breeding date | Expected birthing date |
|---|---|
| 5 Oct 2026 | 28 May 2027 |
| 12 Oct 2026 | 4 Jun 2027 |
| 19 Oct 2026 | 11 Jun 2027 |
| 26 Oct 2026 | 18 Jun 2027 |
| 2 Nov 2026 | 25 Jun 2027 |
| 9 Nov 2026 | 2 Jul 2027 |
| 16 Nov 2026 | 9 Jul 2027 |
| 23 Nov 2026 | 16 Jul 2027 |
| 30 Nov 2026 | 23 Jul 2027 |
| 7 Dec 2026 | 30 Jul 2027 |
| 14 Dec 2026 | 6 Aug 2027 |
| 21 Dec 2026 | 13 Aug 2027 |
Working backwards from a target birthing date
If you want cubs on the ground in a particular week, switch the calculator to target date mode and enter the date you are aiming for. It subtracts 235 days to give the breeding date to book, plus the earliest and latest service dates that still land inside your window.