Sheep Gestation Calculator

The sheep gestation calculator calculates the expected delivery date of your pregnant sheep.

Last updated: January 8, 2026

CreatorFrank Zhao

Mating date 🐑

Lambing date 🐏

🐑

Estimated Arrival Date

Friday, 06/12/2026

147 days to go

Earliest Possible

06/07/2026

Day 142

Latest Possible

06/17/2026

Day 152

ℹ️

Sheep typically deliver within 142 to 152 days. Monitor your sheep closely as the date approaches.

1Lambing date

lambing\_date = mating\_date + 147

mating_dateMating date

lambing_dateLambing date

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Introduction / Overview

The Sheep Gestation Calculator estimates your ewe’s expected lambing date based on a breeding (mating) date. It also shows a practical earliest/latest window, so you can prepare supplies and monitoring in time.

This is useful for flock owners planning lambing pens, nutrition changes, vaccinations, labor coverage, and market timing. If you manage multiple species, you may also like our Goat Gestation Calculator for kidding dates.

✅ Quick note: due dates are estimates. Breed, litter size, and individual variation can shift the true lambing day by several days.

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How to Use / Quick Start Guide

Enter the mating date

Use the Mating date 🐑 field for the day the ewe was bred.

Read the estimated lambing date

The calculator fills in the Lambing date 🐏 and shows an earliest/latest window.

Use it in reverse (optional)

If you have a target lambing date, enter it and the calculator back-solves the mating date.

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Example (with math):

If the ewe was bred on Oct 1, an average lambing estimate uses a 147-day gestation.

\text{Oct 1} + 147\ \text{days}

=

\text{Feb 25}

The earliest/latest range is computed the same way using $142$ and $152$ days.

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Calculation Method / Formula

The calculator uses a standard average sheep gestation length of 147 days, plus a realistic “normal range” window. In the calculator:

Core estimate

\text{Lambing Date} = \text{Mating Date} + 147\ \text{days}

(average; individual pregnancies vary)

Window shown in the results:

Earliest possible: $\text{Mating Date} + 142\ \text{days}$
Latest possible: $\text{Mating Date} + 152\ \text{days}$

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Real-World Examples / Use Cases

Example 1: Planning lambing pen setup

Situation: You record a breeding date of Sep 10 and want a clear prep window.

\text{Sep 10} + 147\ \text{days}

=

\text{Feb 4}

How to use it: Begin stocking supplies and setting up pens at least a week before the “earliest possible” date.

Example 2: Breeding backward from a target lambing date

Situation: You want lambs arriving around Mar 15. When should breeding occur?

\text{Mar 15} - 147\ \text{days}

=

\text{Oct 19}

How to use it: Plan ram turnout or AI dates around the target, then confirm pregnancy and re-check the window.

Example 3: Interpreting “earliest” and “latest”

Situation: Your ewe was bred on Nov 5. What window should you watch most closely?

Earliest

\text{Nov 5} + 142

Average

\text{Nov 5} + 147

Latest

\text{Nov 5} + 152

How to use it: Treat the window as your monitoring period. If you’re outside the range, consider that your breeding date might be off (or consult a vet).

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Common Scenarios / When to Use

Best times to use it

Right after breeding (record keeping)
Before moving ewes into lambing pens
When scheduling help / night checks
Planning vaccinations and nutrition changes

When it may be less accurate

If the breeding date is uncertain (unknown service)
If multiple breeding events occurred across many days
If health issues or extreme stress affected the pregnancy

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Tips & Best Practices

•Write down the date immediately: a “small” recording error of 3–5 days is the most common reason due dates feel off.
•Use the full window: plan your monitoring around the earliest/latest dates, not only the average.
•Prepare supplies early: clean pens, fresh bedding, towels, iodine (if used), and a plan for cold weather.
•Don’t ignore red flags: if the ewe is clearly in trouble, prolonged labor, or shows sudden illness, contact a veterinarian.

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Pro Tip: If you’re timing multiple breeding groups, run the calculator for each group date and write the window on a barn calendar. Small workflow changes often beat perfect math.