Quick answer: Pigs are pregnant for about 115 days, the old “3 months, 3 weeks and 3 days.” Most sows farrow between day 114 and day 117 after first service. Enter the service date in this pig gestation calculator to get the farrowing date for any sow or gilt.
How long are pigs pregnant?
The pig gestation period follows a handy rule: 3 months, 3 weeks and 3 days, which works out to 114 days. Modern sows often run a little longer, at about 115 to 116 days. Most farrow within a day either side of that, and the full normal spread is about 112 to 119 days.
Pig gestation and farrowing date table
Use this table as a quick farrowing or sow gestation calculator. Due dates use 115 days from first service:
| Bred on | Piglets due | Normal window |
|---|---|---|
| Jan 1 | Apr 26 | Apr 25 – Apr 28 |
| Jan 15 | May 10 | May 9 – May 12 |
| Feb 1 | May 27 | May 26 – May 29 |
| Feb 15 | Jun 10 | Jun 9 – Jun 12 |
| Mar 1 | Jun 24 | Jun 23 – Jun 26 |
| Mar 15 | Jul 8 | Jul 7 – Jul 10 |
| Apr 1 | Jul 25 | Jul 24 – Jul 27 |
| Apr 15 | Aug 8 | Aug 7 – Aug 10 |
| May 1 | Aug 24 | Aug 23 – Aug 26 |
| May 15 | Sep 7 | Sep 6 – Sep 9 |
| Jun 1 | Sep 24 | Sep 23 – Sep 26 |
| Jun 15 | Oct 8 | Oct 7 – Oct 10 |
| Jul 1 | Oct 24 | Oct 23 – Oct 26 |
| Jul 15 | Nov 7 | Nov 6 – Nov 9 |
| Aug 1 | Nov 24 | Nov 23 – Nov 26 |
| Aug 15 | Dec 8 | Dec 7 – Dec 10 |
| Sep 1 | Dec 25 | Dec 24 – Dec 27 |
| Sep 15 | Jan 8 | Jan 7 – Jan 10 |
| Oct 1 | Jan 24 | Jan 23 – Jan 26 |
| Oct 15 | Feb 7 | Feb 6 – Feb 9 |
| Nov 1 | Feb 24 | Feb 23 – Feb 26 |
| Nov 15 | Mar 9 | Mar 8 – Mar 11 |
| Dec 1 | Mar 25 | Mar 24 – Mar 27 |
| Dec 15 | Apr 8 | Apr 7 – Apr 10 |
Does gestation length affect the litter?
Yes. Stillbirths become more common when a sow farrows before day 113 or after day 117. Large litters tend to arrive a little sooner, a pattern also seen in guinea pigs. Long farrowings also raise the risk of losing piglets late in the litter.
How can you tell if a sow or gilt is pregnant?
Sows cycle about every 21 days (18 to 24), the same rhythm as the cow heat cycle. A sow that does not come back into heat about three weeks after service is likely pregnant. An ultrasound scan from your vet confirms it. Her belly and udder grow clearly in the last few weeks.
What are the signs a sow is about to farrow?
- Weeks before: her belly grows and the udder swells.
- Last few days: a little colostrum may drip from the teats, and the vulva swells and reddens.
- 12 to 24 hours before: she builds a nest by pawing, rooting the floor and biting at bars.
- Hours before: milk can be stripped from the teats. She gets up and lies down often.
- Close to the first piglet: her breathing speeds up from about 20 to over 60 breaths a minute, and she lies on her side.
How long does farrowing take?
Piglets usually come about 15 to 20 minutes apart, though some arrive faster, and some gaps run past 30 minutes. Each piglet’s cord usually breaks within 5 to 15 minutes, and most find a teat within about 20 minutes. The afterbirth comes out within hours of the last piglet.
Keep a written record of birth times. If more than about 20 to 30 minutes pass while the sow is straining with no piglet, she may need help. Call your vet if you are not trained to assist.
These signs and timings come from a swine reproduction article by Knox and Springer. For other farm animals, see the cattle gestation table or the goat gestation calculator. Our gestation chart compares all of them at a glance.
Frequently asked questions
What is the 3-3-3 rule for pigs?
It is a memory aid for pig pregnancy: 3 months, 3 weeks and 3 days, or about 114 days. Many modern sows farrow a day or two later.
How many months is a pig pregnant?
A little under four months. At 115 days, it is about three and three-quarter months.
Are gilts pregnant for the same time as sows?
Yes. Gilts and sows share the same window of 114 to 117 days, although gilts may have smaller first litters.
Can a sow farrow at 110 days?
It is early. Piglets born well before day 112 may be weak, and stillbirths are more common. Call your vet if she starts farrowing very early.
How soon after farrowing will a sow come back into heat?
Most sows return to heat within about a week after their piglets are weaned, rather than while nursing.
Should I induce farrowing?
Some farms induce to make supervision easier, but early induction raises the risk of weak piglets. Only do it with your vet’s advice and never before the sow’s known average.