Gestation CalculatorSheep Gestation Calculator
Enter the breeding date or the day the ram was turned in. You get the lambing date, the normal window and a check schedule.
Estimated due date
Thu, May 28, 2026
Normal window: May 25, 2026 to Jun 2, 2026
- Today
- Not bred yet
- Days to go
- 147
Pregnancy calendar and key dates
| Date | Day | What to do or expect |
|---|---|---|
| May 14, 2026 | 133 | Start regular checks of the ewe (1 to 2 weeks before) [source] |
| May 25, 2026 | 144 | Normal lambing window opens: have pens, bedding and supplies ready [source] |
| May 28, 2026 | 147 | Estimated due date [source] |
| Jun 2, 2026 | 152 | Normal window closes: call your vet if no birth [source] |
Check with your vet. This is an estimate from average gestation lengths. Your vet can confirm the pregnancy, date it more closely, and tell you when to call for help at birth.
How long is a sheep pregnant?
A ewe is pregnant for about 147 days. New Mexico State University gives a range of 144 to 152 days. That is a spread of about a week, so plan around the whole window, not one day.
NMSU Circular 703 gives 147 days with 144 to 152 days as the range. The Merck Veterinary Manual table lists sheep at 150 days.
| Source | Average | Range |
|---|---|---|
| New Mexico State University | 147 days | 144 to 152 days |
| Merck Veterinary Manual | 150 days | Not given |
How to use the lambing calculator
Enter the first day the rams were with the ewes. The tool adds 147 days for the first likely lambing date and shows the 144 to 152 day window. Run the day the rams came out to see when lambing should end.
NMSU suggests counting the lambing season from the first day rams go in until the day they are taken out.
Ewe due date formula
Lambing date equals breeding date plus 147 days. The window runs from day 144 to day 152. A ewe bred on January 1, 2026 is due about May 28, 2026.
Lambing date = breeding date + 147 days
Lambing checks
NMSU advises checking ewes on a regular basis for 1 to 2 weeks before the expected lambing dates. Once lambing starts, about four checks a day is ideal, with one before 7 a.m. and a final check near dark.
A lamb should arrive within about 30 minutes to 1 hour after the water bag shows. Ewes with twins will show a water bag before each lamb. Call your vet if a ewe makes no progress while you assist.
Questions people ask
How many months is a sheep pregnant?
About five months. 147 days is just under five calendar months.
Why does my book say 150 days?
Merck rounds sheep to 150 days. NMSU gives 147 days on average. Both fall inside the 144 to 152 day window.
Do twins come early?
Our main source does not give a figure for twins, so the tool uses the same window for all ewes.
Other animals
- Cow: 283 days
- Horse: 340 days
- Dog: 63 days
- Goat: 150 days
- Pig: 114 days
- Cat: 65 days
- Rabbit: 31 days
- Alpaca: 342 days
References
- Sheep Production: Birth to Weaning (Circular 703). New Mexico State University, 2022.
- Approximate Gestation Periods (table). Merck Veterinary Manual.