Swine Gestation Calculator by MarkSwine Gestation CalculatorEstimate your sow’s farrowing date and track pregnancy stages. Breeding Date ? Select the date of successful breeding (e.g., 2025-04-01). Gestation Period (days) ? Average is 114 days; range is 112–120 days (e.g., larger litters: ~112, gilts: ~115). Calculate ResetEnter the breeding date, then click “Calculate”. JavaScript is disabled. Please enable it to use the calculator.