How long are sheep pregnant?
About 147 days, a little under five months [7][8][3]. Normal pregnancies run from about 144 to 152 days [7][8], and Alabama Extension gives 147–155 days for lambing [6], so the calculator shows 144 to 155 days.
| Source | What it says |
|---|---|
| New Mexico State Extension [7] | About 147 days; 144–152 |
| Montana State Extension [8] | Average 144–151 days depending on breed (about 147); single ewes 138–159 |
| Merck Vet Manual [3] | Average 147 days (Merck’s summary table rounds to 150) |
| Alabama Extension [6] | Lambing and kidding usually 147–155 days after conception |
Merck’s one-line summary table rounds sheep to 150 days [1]. Its full sheep chapter, and every extension service we checked, use 147 [3][7][8], so that is the average here.
Breed makes a difference
Montana State notes that prolific breeds such as the Finn have shorter pregnancies and slow-maturing fine-wool breeds such as the Rambouillet longer ones, and that ewes within a breed can differ by 3 to 5 days [8]. If you know your flock usually lambs early or late, expect the same this year.
Worked example: lambing window for a flock
A ewe’s heat cycle is about 17 days [3][8][6], so rams left in for 34 days get two chances at each ewe. With rams in on October 1, 2026 and out on November 4, 2026:
- Average lambing dates: February 25, 2027 (ewes bred on day one) to March 31, 2027 (bred on the last day).
- Earliest and latest possible lambs: February 22, 2027 to April 8, 2027.
- Best days to scan and count lambs: November 15, 2026 to December 24, 2026.
NMSU suggests checking ewes regularly from 1 to 2 weeks before the expected date [7]; the calendar marks that window.
Scanning and pregnancy checks
| When | What |
|---|---|
| Day 14–20 | Watch for a return to heat. Ewes cycle about every 17 days (14–20), so an open ewe shows heat again around then. [2][6][8] |
| Day 25–30 | Blood pregnancy test possible. Accurate from about 25–30 days after breeding. (per Penn State Extension) [5] |
| Day 31 | Ultrasound through the belly. Can show a pregnancy from about day 30–31. [4][5] |
| Day 45–50 | Best time to count lambs by ultrasound. Days 45–50 are best for counting; counts get harder after about day 85. [4][5] |
| 7–14 days before the due date | Start checking ewes often. Check ewes regularly from 1–2 weeks before the expected lambing date. (per NMSU Extension) [7] |
A belly scan is more than 80% accurate after day 31 [4]. Days 45–50 are the best time to count lambs, because the placentomes are easy to see and the lambs aren’t yet too big [4]. Penn State puts the most accurate scan around day 45, with counts possible up to about day 85 [5].
Common questions
How many months is a sheep pregnant?
About 4.8 months: 147 days, or 21 weeks.
When do sheep come into heat?
Sheep are seasonal breeders: most cycle from early autumn into winter [2][3]. A ewe is in heat for about 24–36 hours of each 17-day cycle[6][8].
Can I work out the lambing date from the raddle mark?
Yes. If your rams wear a marking harness, the day a ewe is first marked is when she was mated: enter it as the first date and leave the second blank.
Do twins come earlier?
Prolific breeds, which often carry twins and triplets, have shorter average gestations [8]. The sources we used don’t give a separate figure for twin pregnancies, so the calculator uses the same range.
These dates are planning estimates from published averages, not veterinary advice. Your vet or a scanner can confirm pregnancies and lamb counts.
Sources
- Merck Veterinary Manual, table “Approximate Gestation Periods”Gestation by species; dog 62–64 days from ovulation, 58–72 days from breeding
- Merck Veterinary Manual, table “Features of the Reproductive Cycle”Estrous cycle lengths (cattle 18–24, sheep 14–20 days); dog puberty 6–24 months
- S. G. Balch, “Breeding, Parturition, and Common Lamb Diseases of Sheep,” Merck Veterinary ManualSheep gestation averages 147 days; 17-day cycle
- C. M. Scully, “Pregnancy Determination in Ewes,” Merck Veterinary Manual (reviewed 2026)Ultrasound accuracy after 31 days; fetal count best at 45–50 days
- C. Hill, “Are There Any Buns in the Oven? Methods of Pregnancy Testing in Small Ruminants,” Penn State ExtensionBlood tests at 25–30 days; ultrasound from 20 or 30 days, best near 45, counting to 85; 19–24-day cycle
- B. Brady, “Reproductive Management—Dairy Goats and Sheep,” Alabama Cooperative Extension System (2019)Goat gestation 150 days; kidding and lambing 147–155 days; cycles; ultrasound at 32 days; breeding table
- Pitassi et al., “Sheep Production: Birth to Weaning,” NMSU Circular 703 (2022)Ewe gestation about 147 days (144–152); check ewes 1–2 weeks before
- R. Kott, Montana Farm Flock Sheep Production Handbook, “Reproduction,” Montana State University ExtensionAverage 144–151 days by breed (about 147); individuals 138–159; 17-day cycle