Swine Gestation Calculator
Plan farrowing with confidence. This Pig Gestation Calculator adds the standard 115 days to your breeding date and shows a practical ±2-day window. You also get a day-by-day status line and a farm-ready timeline of checks, scans, and pre-farrowing tasks.
How the Swine (Pig) Gestation Calculator works
Most farms schedule swine gestation at 115 days. That old saying “3 months, 3 weeks, and 3 days” still holds up. Enter the breeding date and the calculator outputs an estimated farrowing date plus a short window on either side.
The simple formula
- Estimated farrowing date (EFD): breeding date + 115 days.
- Window: two days before the EFD and two days after.
- Status line: shows “X days into gestation” and a live countdown to the EFD.
Why we use a ±2-day window
Gestation varies slightly by litter size, season, and parity. A concise ±2-day window keeps planning tight without false precision.
Ultrasound and heat checks
Pregnancy checks pair nicely with the calculator. Many operations scan around day 24–30. Heat detection also matters in days 18–25 after breeding since a return often lands in that span.
Why accurate timing matters
Small timing errors can snowball. You load sows too late and you scramble. You vaccinate too early and protection wanes. You feed too little in late gestation and farrowing gets harder.
A reliable due date stops the guesswork. Farrowing rooms get prepped on time. Staff rosters line up with peak farrowings. Feed and vaccines hit the right windows.
Gestation timeline & milestones
Use this table to plan the weeks between breeding and farrowing. It matches what the calculator shows on screen.
| Milestone | Typical timing | What you do |
|---|---|---|
| Return-to-estrus check | Days 18–25 post-breeding | Watch for standing heat and behavior changes. Rebreed if needed. |
| Pregnancy ultrasound | Days 24–30 | Confirm pregnancy with B-mode ultrasound. Re-check borderline results a few days later. |
| Increase energy ration (“bump feed”) | From about day 100 | Raise feed gradually based on body condition and herd protocol. |
| Pre-farrowing booster | 14–21 days before EFD | Give the second dose per label and vet advice. Keep records tight. |
| Move to farrowing area | 5–10 days before EFD | Shift to farrowing rooms and finish pen prep. Stage supplies. |
| Expected farrowing | EFD ± 2 days | Watch closely. Keep clean towels, lube, iodine, and heat sources ready. |
Notes on variation
- Litter size: larger litters sometimes run a touch longer. Smaller litters can arrive a bit earlier.
- Seasonality: heat stress and day length can nudge timing.
- Parity: gilts often need closer monitoring as due dates approach.
How to use the tool
- Pick your breeding date in the date field.
- Read the Estimated farrowing date in the blue result card.
- Note the Practical window and add it to your calendar.
- Scroll to see the Timeline & milestones box and schedule tasks.
- Tap Copy to share the result with your team.
Accessibility and mobile tips
- The date fields use the device’s native picker.
- Buttons have clear labels and large touch targets.
- The result card is live-updated and uses polite ARIA announcements.
Examples you can copy
Here are three sample scenarios. Yours will shift with the breeding date you enter.
What if the scan says “open” at day 24
That can happen. Scan again a few days later. Day-24 images can be equivocal when ovulation lagged or fluid volume is low.
Practical tips for record-keeping
- Capture everything on day zero. Boar ID, semen batch, parity, and your breeding time window.
- Set automated reminders. Create calendar alerts for scan, feed change, booster, and move-in dates.
- Track body condition. Photograph or score weekly in late gestation and adjust feed in small steps.
- Stage farrowing kits. Heat source, clean towels, lube, disinfectant, navel iodine, cords, and a scale.
- Make downtime notes. Jot issues after each farrowing and feed them back into SOPs.
FAQ: quick answers
What is the normal swine gestation length?
Most sows farrow around 115 days after breeding. A normal range runs from about 113 to 117 days.
Why does the calculator use a ±2-day window?
It reflects practical variation. The window is tight enough for scheduling and flexible enough to fit herd-level differences.
Do gilts and multiparous sows share the same due date rules?
The 115-day target applies to both. Gilts sometimes need more hands-on prep near term.
When should I move sows to farrowing rooms?
Plan on 5–10 days before the estimated farrowing date. That gives time to acclimate and to finish setup.
When do you increase feed?
Many programs bump feed from about day 100 to farrowing. Always match changes to body condition.
When is pregnancy ultrasound most reliable?
Scanning after day 24 is safer. Borderline images should be re-checked within a few days.
What if she returns to heat?
Watch days 18–25 after breeding. If she stands again then she probably isn’t pregnant.
Do ovulation-based dates change the output?
For most farms the practical farrowing window stays the same. Use breeding dates for scheduling unless your vet says otherwise.
