Enter a ewe's breeding date for the lambing due date — or reverse it and enter the lamb's birth date to find the breeding window.
A ewe's gestation averages about 147 days — roughly five months. It varies from about 142 to 152 days depending on breed, litter size, and the individual ewe, so the due date is an estimate. This calculator adds 147 days to the breeding date for the expected lambing date.
Already have lambs on the ground? Switch to reverse mode and enter the birth date. The calculator subtracts about 147 days to estimate the breeding date and shows a breeding window — useful for confirming the exposure date and the likely sire.
Gestation varies by breed and litter, so treat this as a general estimate for flock planning, not veterinary advice. Source: average ovine gestation ~147 days (142–152 day range) per sheep breed and production references.