Pig Gestation Calculator
Enter a breeding date to get your sow’s expected farrowing date.
A sow is pregnant for about 114 days. That is 3 months, 3 weeks and 3 days. Add 114 days to the breeding date to get her expected farrowing date, and allow 2 days either side.
How to use the pig gestation calculator
- Pick the breeding date. If you bred over several days, many producers use the first day or the middle day. Choose one method and stick with it.
- Leave gestation length at 114 days unless your records show a different average for your herd.
- Press Calculate farrowing date.
- Read the expected date, the normal window and the checkpoints along the way.
Need a different length? Pick a preset from 112 to 116 days. Or choose Custom value and enter a whole number from 100 to 130.
How the calculation works
The maths is simple. The tool takes your breeding date and counts forward by the gestation length. The standard figure is 114 days. Certified Pedigreed Swine gives it as 114 days, plus or minus 2 days.
The tool then shows a window. The window runs from 2 days before the expected date to 2 days after it. Most sows farrow inside it.
It also lists checkpoints counted from the breeding date:
- Day 21: a sow that does not return to heat may be pregnant.
- Day 30: ultrasound confirmation is possible.
- Day 90: a common time to move the sow to a farrowing pen.
- Day 110: start final farrowing preparation.
These checkpoints follow the FarmKeep milestone table. Your farm plan or vet may use different timing.
Worked example
You breed a sow on January 1, 2025. You use the standard 114 days.
- January 1 plus 31 days is February 1.
- Add 28 more days for February and you reach March 1. That is day 59.
- Add 31 days and you reach April 1. That is day 90.
- Add 24 more days and you reach April 25. That is day 114.
Her expected farrowing date is Friday, April 25, 2025. The window runs from April 23 to April 27. Day 21 falls on January 22. Day 30 is January 31. Day 90 is March 31. Day 110 is April 21.
Pig gestation reference table
| Breeding date | Farrowing at 112 days | Farrowing at 114 days | Farrowing at 116 days |
|---|---|---|---|
| January 1, 2025 | April 23, 2025 | April 25, 2025 | April 27, 2025 |
| March 10, 2024 | June 30, 2024 | July 2, 2024 | July 4, 2024 |
| December 15, 2025 | April 6, 2026 | April 8, 2026 | April 10, 2026 |
Key days after breeding:
| Day | What it means |
|---|---|
| 21 | Check whether the sow returns to heat |
| 30 | Ultrasound confirmation possible |
| 90 | Common time to move to a farrowing pen |
| 110 | Begin final preparation |
| 114 | Average farrowing date |
Tips and common mistakes
- Do not treat day 114 as a deadline. A 2-day swing either way is normal.
- Use the right breeding date. If a sow was bred more than once, mark which date you counted from. Mixing methods shifts your dates.
- Confirm pregnancy. A date on a calculator does not mean the sow is pregnant. Check for a return to heat around day 21, and consider an ultrasound after day 30.
- Prepare early. Clean the pen and gather towels, iodine, a heat lamp and record sheets before day 110.
- Know the signs. Nesting, restlessness, a swollen vulva and milk production can show that farrowing is close.
- Keep records. If your own herd averages a different length, note it. [CHECK: confirm whether any breed has a commonly published gestation length that differs from 114 days.]
- Ask your vet. If a sow runs past her window or seems unwell, call a vet. This calculator is not veterinary advice.
Keeping several species? We have calculators for the cow, the goat and the sheep.
FAQ
How do you calculate pig pregnancy?
Add 114 days to the breeding date. That gives the expected farrowing date. Many farms count the first day of breeding, or the middle of a multi-day breeding, as day zero. Pick one method and use it every time.
What is the 3-3-3 rule for pigs?
It is a memory aid for pig gestation: 3 months, 3 weeks and 3 days. That adds up to about 114 days.
How many months are pigs pregnant for?
A sow is pregnant for about 3 months, 3 weeks and 3 days. That is roughly 3.75 months, or 114 days.
What is the gestation calendar for sows?
It is a table that lists the farrowing date for each breeding date, using 114 days. This calculator does the same job for any date you enter, and it also lists the checkpoints along the way.
Can a sow farrow before or after day 114?
Yes. Gestation commonly varies by about 2 days either way, so farrowing from day 112 to day 116 is normal. Call your vet if a sow is well past her window or shows signs of trouble.
When should I move a sow to the farrowing pen?
One ranking guide suggests around day 90, and it also says days 90 to 100 are common. Follow your own herd plan and your vet’s advice. [CHECK: confirm timing against a university extension guide.]