Pig Gestation Calculator

How to Use This Calculator

Enter the date your sow was bred or artificially inseminated. Select the breed if known — though swine breeds have very similar gestation lengths, ranging from 113–115 days. Click Calculate Due Date to see the expected farrowing date and a full milestone timeline.

The calculator stores your last entry in the browser, making it easy to track multiple sows during peak breeding and farrowing seasons.

Pig Gestation Period — What to Expect

The gestation period for pigs is one of the most predictable in livestock at exactly 114 days (range: 112–116). The question of how long is a pig's gestation period is one of the easiest to remember in all of livestock production — it's exactly 3 months, 3 weeks, and 3 days. The consistency of the gestation period of pigs makes production scheduling highly reliable, which is one reason commercial pig farming operates on tight all-in/all-out cycles.

Days 1–30 (Early gestation): Embryos implant in the uterine horns around days 12–18. This is the most critical period — heat stress, mycotoxins, or nutritional deficiencies during early gestation can cause embryo loss. Feed gestation-specific rations and maintain comfortable temperatures.

Days 30–85 (Mid-gestation): Fetal development continues at a steady pace. Pregnancy can be confirmed by ultrasound at day 25–30 or by return-to-estrus check at day 18–24. Maintain sow body condition score (BCS 3–3.5) throughout this period.

Days 85–114 (Late gestation): Rapid fetal growth occurs, with 60–70% of final birth weight gained in the last 4 weeks. Increase feed intake in the final 2 weeks (flushing) to maximize colostrum and milk production. Move the sow to the farrowing house at day 107–110.

Research from Iowa State University Extension and USDA shows that farrowing rate and litter size are strongly influenced by gilt age at first service, BCS at breeding, and heat stress management — particularly critical in summer months.

Breed-Specific Pig Gestation Periods

The 3-3-3 Rule — Explained

The 3-3-3 rule is the classic mnemonic for pig gestation: 3 months + 3 weeks + 3 days = 114 days. It's one of the most memorable facts in all of livestock production. Here's the breakdown:

Signs of Pig Pregnancy

Confirming pregnancy early helps reduce open sow days and improve production efficiency. Here are the key signs and confirmation methods:

• →No return to estrus (days 18–24): The most common field check. A sow that does not show heat at her expected estrus window is presumed pregnant.
• →Ultrasound (days 25–35): Real-time ultrasound can detect fluid-filled uterine horns at day 25 and embryos at day 28–30. Most reliable confirmation method.
• →Belly enlargement (days 80+): Visible abdominal enlargement becomes apparent in the final month, especially in gilts with smaller litters.
• →Mammary development (day 100+): Udder begins to develop noticeably. Waxing of the teats typically occurs 12–24 hours before farrowing.
• →Nesting behavior (day 110–114): Sows often root bedding and show restlessness as farrowing approaches.

Farrowing Checklist

Move sows to the farrowing crate at day 107–110 (1 week before expected farrowing). Use this checklist to prepare:

Frequently Asked Questions

Sources & References

• USDA NASS — Hog and pig production statistics
• Penn State Extension — Swine reproduction and farrowing management
• University of Minnesota Extension — Swine gestation and production
• Merck Veterinary Manual — Porcine reproduction

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