Animal Gestation Calculator

Sheep Gestation Calculator

A sheep's gestation period is about 147 days, or roughly 4 months and 3 weeks, though it ranges from 144 to 152 days depending on breed and individual animal.

How to use the sheep gestation calculator

  1. 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. 2. Refine the inputs. Pick the breed so the calculator uses the right average gestation length.
  3. 3. Plan around the range. Use the earliest and latest dates and the milestone timeline to schedule checks, feed changes and preparation of the lambing area.

Calculate a lamb due date

What do you know?

Estimated lambing date

Saturday, 6 February 2027

Earliest

3 Feb 2027

Latest

11 Feb 2027

147 days remaining0% complete

0 of 147 days elapsed

Milestone timeline

Key Sheep pregnancy milestones with calculated calendar dates
DayMilestoneDate
17Ewe returns to heat if not in lamb — watch the ram's marks29 Sept 2026
45Scanning window opens: ultrasound counts lambs from day 45 to 9027 Oct 2026
100Split the flock by lamb count and lift the ration for twins and triplets21 Dec 2026
125Clostridial and pasteurella booster so colostrum carries antibodies15 Jan 2027
135Crutch or dag the ewes and move them to the lambing paddock or shed25 Jan 2027
147Expected lambing6 Feb 2027

What to do next

How long is a sheep's gestation period?

The average is 147 days from breeding to lambing, about 4 months and 3 weeks. Anything between 144 and 152 days is normal, and a typical litter is 1-2 lambs. Treat the calculated date as the middle of that window rather than a fixed appointment.

Sheep gestation table: breeding date to lambing date

Breeding dates one week apart with the matching lambing date at 147 days.

Twelve sample Sheep breeding dates and their calculated due dates
Breeding dateExpected lambing date
12 Sept 20266 Feb 2027
19 Sept 202613 Feb 2027
26 Sept 202620 Feb 2027
3 Oct 202627 Feb 2027
10 Oct 20266 Mar 2027
17 Oct 202613 Mar 2027
24 Oct 202620 Mar 2027
31 Oct 202627 Mar 2027
7 Nov 20263 Apr 2027
14 Nov 202610 Apr 2027
21 Nov 202617 Apr 2027
28 Nov 202624 Apr 2027

How breed changes the lambing date

Selecting a breed swaps the average the calculator uses, which can move the lambing date by more than a week.

Sheep breeds and their average gestation length in days
BreedAverage daysDifference
Average147—
Finnsheep143-4 days
Romanov144-3 days
Dorset145-2 days
Suffolk145-2 days
Texel147—
Merino148+1 days
Rambouillet149+2 days
Border Leicester149+2 days
Karakul150+3 days

Working backwards from a target lambing date

If you want lambs on the ground in a particular week, switch the calculator to target date mode and enter the date you are aiming for. It subtracts 147 days to give the breeding date to book, plus the earliest and latest service dates that still land inside your window.

Sheep gestation calculator FAQs

How long is a sheep pregnant?

About 147 days, which is roughly five months, with a normal range of 142 to 152 days. Prolific breeds such as Finnsheep lamb closer to 143 days and fine-wool breeds such as Merino closer to 148.

Does breed change a ewe's gestation length?

Yes, by up to a week across the extremes. The table above lists common breeds: Finnsheep and Romanov at 143 to 144 days through to Karakul at about 150. Sire breed matters as well because the lamb's own genes help trigger labour.

When can a ewe be scanned to see how many lambs she is carrying?

Between day 45 and day 90 after mating. Earlier than 45 days and litter counts are unreliable; much later and the lambs are too large to count on screen. Scanning results let you feed singles, twins and triplets separately, which is the single most profitable job in the whole pregnancy.

How much extra feed does a pregnant ewe need?

Almost nothing extra for the first 90 days, then a steep climb. In the last six weeks a twin-bearing ewe needs roughly 1.8 to 2 times her maintenance energy, and a triplet-bearing ewe more still. Underfeeding now causes twin lamb disease, small lambs and poor colostrum.

What are the signs a ewe will lamb tonight?

She leaves the flock, paws and circles a spot in the bedding, lies down and stands repeatedly, and her vulva is soft and swollen with the udder tight. A visible mucus string usually means the first lamb arrives within a few hours; if she strains hard for more than an hour with no lamb, examine her or call your vet.

More gestation pages

Livestock gestation chart