Sheep Pregnancy Calculator - Estimate Lambing Date
Sheep Gestation Calculator
This calculator helps you estimate a ewe’s expected lambing date from a known breeding (mating) date. It also provides a practical due-date window (early to late) and a week-by-week planning timeline you can export to CSV or Excel.
How the calculation works
The core estimate is based on an average gestation length in days. You can adjust the average for your flock if you have historical records.
Estimated lambing date is computed as:
\[\text{Due Date}=\text{Breeding Date}+\text{Gestation Days}\]
Lambing window is computed using a variation value (± days):
\[\text{Window Start}=\text{Breeding Date}+(\text{Gestation Days}-\text{Variation Days})\]
\[\text{Window End}=\text{Breeding Date}+(\text{Gestation Days}+\text{Variation Days})\]
How to use the planning timeline
The table breaks the pregnancy into weekly blocks. Each week shows:
Start date and end date for that week, plus a simple milestone label and planning notes.
This is designed for general planning such as staffing, pen readiness, and supply checklists. For flock health decisions and local protocols, always follow your veterinarian or local extension guidance.
Tips for more accurate estimates
Use your flock’s historical average if you track actual lambing dates. Over time, your own records will typically outperform generic averages.
Set a realistic variation (± days) so your planning window reflects real-world spread across ewes.
Export the schedule to share with staff, set reminders, or coordinate busy lambing periods.
Notes and limitations
This calculator provides planning estimates and does not diagnose pregnancy or predict complications. Outcomes can vary by breed, litter size, ewe condition, and management environment.