Add the classic 114-day pig gestation ("3 months, 3 weeks, 3 days") to a breeding date to plan farrowing — or work back from a farrowing week.
Use this when you bred a sow or gilt by AI or hand-mating and need a farrowing date to move her into the farrowing pen, set up heat lamps, and plan litter processing.
Most sows farrow within a few days of 114 days. Gilts and large litters can shift the date slightly, so plan a short window rather than a single day.
Forward mode adds gestation days to the breeding date. Reverse mode subtracts gestation days from the date you want sows to farrow. The 114-day default is the standard swine planning figure; change it if your herd records differ.
farrowing_date = breeding_date + gestation_days
breeding_date = target_farrowing_date − gestation_days
window = result ± window_days
Bred 10 Jun 2026 at 114 days → due about 2 Oct 2026. With a ±3 day window, watch roughly 29 Sep 2026 – 5 Oct 2026.
Reverse check: to have sows farrow on 2 Oct 2026, breed on 10 Jun 2026 (2 Oct 2026 − 114 days).
Assumptions: calendar-day arithmetic from a single breeding date; gestation length is a planning average you can change.
Limits: Repeat services and missed heats change the true conception date. Not a pregnancy diagnosis and not veterinary advice.
Responsibility: confirm pregnancy with your veterinarian and have facilities and supplies ready before the early edge of the window.
It is a memory aid that lands close to 114 days. Calendar months vary in length, so counting days is more reliable — that is what this calculator does.
Use the first mating date for the early edge and the second for the late edge, or enter the first date with a window of 3–4 days.
Many producers move sows several days before the due date so they settle in. Follow your own facility plan and veterinarian advice.