Pig Gestation Calculator
Farrowing due date and window from breeding date.
What it does
Pig gestation is famously steady at 114 days, remembered as 3 months, 3 weeks, and 3 days. Breeders count forward from first boar exposure, then ready the farrowing pen against that date rather than against behavior signs alone.
The tool above takes the breeding date and a herd average. It returns the due date with the 111 to 117 day normal window beside it, so feed increases, pen moves, and night checks land on schedule.
The default breeding of October 10 2026 gives a due date of Monday February 01 2027, with the window running Friday January 29 to Thursday February 04 2027. A 115 day average moves the due date to Tuesday February 02 2027.
These figures follow Purdue extension swine guidance with Missouri extension matching it: 114 days average with a 114 day gestation table for planning. Both describe the same 3-3-3 count used across breeds and parities.
How to use
- Enter the first date with the boar.
- Keep 114 unless herd records say otherwise.
- Read the farrowing due date.
- Move sows to clean pens near day 110.
- Start night checks when the window opens.
- Call the vet past day 117.
Formula
- avg
- Herd average gestation in days, default 114.
- 111
- Day the normal window opens.
- 117
- Day the normal window closes; vet call past this.
All dates compute in UTC so time zones never shift a day. Gilts trend slightly early while mature sows hold closer to 114, which is why the average stays adjustable inside a fixed 111 to 117 window.
Worked example
Example: bred October 10 2026
Breeding date 2026-10-10, average 114 days.
- Due: Oct 10 + 114 days = Feb 1 2027.
- Early: Oct 10 + 111 = Jan 29 2027.
- Late: Oct 10 + 117 = Feb 4 2027.
- Check: 21 left in Oct, plus 30, 31, 31, plus 1 in Feb = 114.
- 115 day average: Oct 10 + 115 = Feb 2 2027.
- Tool shows Mon Feb 01 2027, window Fri Jan 29 2027 to Thu Feb 04 2027.
Reference table
| Day | Mark | Action |
|---|---|---|
| 30 | Pregnancy check | Ultrasound |
| 90+ | Raise feed | Late gestation |
| 110 | Move to farrowing | Clean, bedded pen |
| 111 | Window opens | Night checks |
| 114 | Due date | 3-3-3 average |
| 117 | Window closes | Call vet past this |
Limits
- Breeding dates predict well but never exactly.
- Gilts and small litters shift timing.
- Heat stress and thin feed scatter dates.
- Calendar math never beats udder and behavior signs.
Common mistakes
- Treating the due date as exact.
- Skipping the day 30 pregnancy check.
- Moving sows into farrowing too late.
- Feeding late gestation like early gestation.
- Waiting past day 117 to call the vet.
Try it yourself
Quick checks. Answers sit tucked under each question.
Bred Nov 1 2026: due date?
Nov 1 + 114 = Tue Feb 23 2027.
Same breeding at 115 days?
Window Jan 29 to Feb 4 shifts with it; due moves a day later.
Why plan the window, not the day?
Gilts, litter size, and feed scatter farrowing across 111 to 117 days.
Questions
How long are pigs pregnant?
About 114 days on average, 111 to 117 days normally.
What is the 3-3-3 rule?
3 months, 3 weeks, 3 days: the old way to remember 114 days.
When to move to farrowing?
Near day 110 into a clean, bedded, draft free pen.
Gilts different?
Often a touch early with smaller litters; watch them closer.
What if day 117 passes?
Call the vet; overdue sows need checking, not waiting.
Feed changes when?
Raise rations in late gestation for fast fetal growth.