Last updated: May 25, 2026
Swine Gestation Calculator
Creators
Dharmendra SinghReviewers
Creators
Dharmendra SinghReviewers
Quick Answer
Calculate pig farrowing date using the classic 3 months, 3 weeks, 3 days (114 days) rule. The formula used is Due Date = Breeding Date + 114 days (3-3-3). The Swine Gestation Calculator uses the classic farmer's rule: 3 months, 3 weeks, 3 days = 114 days.
Calculate pig farrowing date using the classic 3 months, 3 weeks, 3 days (114 days) rule.
Key Takeaways
- Pig gestation is 114 days — the classic '3 months, 3 weeks, 3 days' (3-3-3) rule
- Move sow to farrowing area by day 110 — reduce feed to 50% to prevent constipation/MMA
- Colostrum within 6 hours is critical — piglets have ZERO immune protection at birth
- First 30 days are the highest-risk for embryo loss — minimize all stress during implantation
- Commercial sows average 10-14 piglets; heritage breeds average 8-10 per litter
Creators
Dharmendra SinghReviewers
Creators
Dharmendra SinghReviewers
Formula
Due Date = Breeding Date + 114 days (3-3-3)
Where:
- D_{farrow}=Expected farrowing date(date)
- D_{breeding}=Date sow was bred(date)
- 114=Porcine gestation (3 months, 3 weeks, 3 days)(days)
Worked Examples
Yorkshire Sow — Standard (3-3-3)
A Yorkshire sow bred on March 1, 2026
- 1Breeding date: March 1, 2026
- 2Yorkshire gestation: 114 days (3 months, 3 weeks, 3 days)
- 3Due date = March 1 + 114 days = June 23, 2026
Berkshire — Longer Gestation
A Berkshire sow bred on April 1, 2026
- 1Breeding date: April 1, 2026
- 2Berkshire gestation: 116 days
- 3Due date = April 1 + 116 days = July 26, 2026
Pietrain — Slightly Shorter
A Pietrain sow bred on May 15, 2026
- 1Breeding date: May 15, 2026
- 2Pietrain gestation: 113 days
- 3Due date = May 15 + 113 days = September 5, 2026
Introduction
The Swine Gestation Calculator uses the classic farmer's rule: 3 months, 3 weeks, 3 days = 114 days. This mnemonic has been used for centuries and remains remarkably accurate. Porcine gestation ranges from 111-117 days depending on breed and litter size. Accurate farrowing prediction allows proper preparation of the farrowing crate/pen, colostrum management, and piglet care. For other livestock calculators, see our cow gestation calculator and goat gestation calculator.
Swine Pregnancy Stages
The 114-day gestation is divided into three phases with distinct management priorities.
- Days 1-40 (Implantation):
Critical period — embryos implant by day 12-14. AVOID stress, fighting, transport, and temperature extremes. Keep sow calm. Embryonic mortality highest in first 30 days.
- Days 41-80 (Fetal Growth):
Organ development and skeletal growth. Maintain body condition score 3.0. Normal exercise and group housing OK. Ultrasound at day 25-30 confirms pregnancy.
- Days 81-114 (Rapid Growth):
Piglets gain 65% of birth weight in final 5 weeks. Increase feed by 30% in last 2 weeks. Move to farrowing area by day 110. Wash sow before moving.
Gestation by Pig Breed
Breed affects gestation ±2-3 days, with heritage breeds tending slightly longer.
| Breed | Avg (days) | Range | Avg Litter |
|---|---|---|---|
| Pietrain | 113 | 111-115 | 9-11 |
| Yorkshire | 114 | 112-116 | 10-14 |
| Landrace | 114 | 112-116 | 10-14 |
| Hampshire | 114 | 112-116 | 8-12 |
| Duroc | 115 | 113-117 | 9-12 |
| Berkshire | 116 | 114-118 | 8-10 |
| Large Black | 116 | 114-118 | 8-10 |
| Pot-Bellied (pet) | 114 | 112-116 | 4-8 |
Farrowing Preparation
Proper preparation in the final week prevents piglet death and sow complications.
- Day 107-110:
Move sow to clean, disinfected farrowing area. Wash sow with mild soap before moving.
- Farrowing crate/pen:
Anti-crush bars to prevent sow lying on piglets, heated creep area (90°F/32°C for piglets), non-slip floor
- Day 110-112:
Reduce feed to 50% to prevent constipation and MMA (mastitis-metritis-agalactia)
- Have supplies ready:
towels, iodine for navels, oxytocin (vet prescription), heat lamps, tube feeding supplies
- Creep heating:
Piglets need 90°F (32°C) in first week — heat lamp or heat pad in creep area
- Day 113+:
Monitor sow every 2-4 hours for signs of imminent farrowing
Signs of Imminent Farrowing
Sows give reliable signs in the final 24-48 hours before farrowing.
- 2-3 days before:
Vulva swells and reddens, udder line fills with milk
- 12-24 hours before:
Milk can be expressed from teats (colostrum), restlessness, nesting behavior
- 6-12 hours before:
Sow lies down, gets up, lies down repeatedly. Chews on bedding/bars. Breathing rate increases.
- Active labor:
Tail twitches, visible contractions (flanks contract rhythmically). First piglet within 1-2 hours.
- Normal delivery:
Piglets arrive every 15-30 minutes. Total farrowing 2-5 hours for 10-12 piglets.
- Afterbirth:
Placentas expelled 1-4 hours after last piglet. Two placentas normal (bicornuate uterus).
Milk expressible from teats = farrowing within 24 hours. This is the most reliable predictor.
Newborn Piglet Care (First 24 Hours)
The first 24 hours determine piglet survival — hypothermia and crushing are top killers.
- Colostrum:
Piglets MUST receive colostrum within 6 hours of birth (antibodies + energy). Gut closes to IgG absorption within 24-36 hours.
- Navel care:
Dip in iodine solution immediately to prevent navel infections
- Warmth:
Piglets are born with almost no fat — heat lamp/pad essential. Target 90°F (32°C) in creep area.
- Split suckling:
If 14+ piglet litter, rotate access to sow in groups of 6-8 to ensure all get colostrum
- Iron injection:
Piglets need iron (FeDex) at day 1-3 to prevent anemia (sow's milk is iron-deficient)
- Teeth:
Clip needle teeth to prevent teat damage if litter is large and competitive
Feeding the Pregnant and Lactating Sow
Feed level changes dramatically across gestation. Overfeeding in early-to-mid pregnancy reduces litter size and milk yield, while the last weeks and lactation demand far more energy.
| Stage | Daily Feed | Goal |
|---|---|---|
| Days 1-30 | 1.8-2.2 kg (moderate) | Protect implantation; avoid overfeeding |
| Days 31-90 | 2.0-2.5 kg | Maintain body condition score ~3.0 |
| Days 91-110 | 2.5-3.5 kg (+30%) | Support rapid fetal growth & udder development |
| Days 110-114 | ~1.5 kg (reduced) | Prevent constipation and MMA at farrowing |
| Lactation | Free-choice (5-8 kg) | Peak milk output; protect sow body reserves |
Add bulky fiber (beet pulp, bran) in the last week and ensure unlimited water — constipation around farrowing is a major trigger for MMA.
Weaning and Rebreeding Schedule
Sows are typically rebred after weaning, not after farrowing. A predictable wean-to-estrus interval keeps the herd's farrowing schedule tight.
Wean piglets at 21-28 days in most commercial systems (heritage/pet keepers often later)
Sows return to standing heat 3-7 days after weaning (average ~5 days)
Breed on the post-weaning heat for the best conception and litter size
This cadence yields about 2.3-2.5 litters per sow per year
Maintain a sow productive life of 5-6 years (roughly 6-10 litters)
Flush feeding (extra energy) before breeding can boost ovulation rate
Quick Reference Card
Swine Gestation — Quick Reference (3-3-3 Rule)
Quick reference • Swine Gestation Calculator
Due Date = Breeding Date + 114 days (3 months + 3 weeks + 3 days)Valid range: 111–117 days depending on breed
Common Values
⚠ Watch Out
- •No piglet after 45+ minutes of active straining = veterinary intervention needed
- •Reduce feed to 50% from day 110 or risk MMA (mastitis-metritis-agalactia)
- •Piglets without colostrum in 6 hours = 50%+ mortality — monitor first nursing
- •Piglet crushing #1 killer — ensure anti-crush bars or sloped walls in farrowing area
Pro Tips
- →Milk expressed from teats = farrowing within 24 hours (most reliable sign)
- →Iron injection (200mg FeDex) at day 1-3 prevents fatal piglet anemia
- →Heat lamp at 90°F (32°C) in creep area — piglets have zero fat reserves at birth
- →Split suckling for 14+ litters: rotate groups of 6-8 to ensure all get colostrum
FAQs
How long are pigs pregnant?
Pigs are pregnant for 114 days on average — remembered as '3 months, 3 weeks, and 3 days' (the classic 3-3-3 rule). The range is 111-117 days depending on breed, with heritage breeds (Berkshire, Large Black) going 116 days and modern crosses averaging 114.
What does the '3-3-3 rule' mean?
The 3-3-3 rule is a mnemonic for pig gestation: 3 months + 3 weeks + 3 days = approximately 114 days. It's been used by pig farmers for centuries as a simple way to calculate farrowing dates without a calculator. It remains remarkably accurate.
How many piglets can a sow have?
Commercial sows (Yorkshire, Landrace) average 10-14 piglets per litter. Heritage breeds average 8-10. The record is 27 piglets in a single litter. Prolific genetics have pushed modern sow averages to 14+ in many commercial herds. Sows have 12-16 functional nipples.
When should I move the sow to the farrowing area?
Move the sow to the clean farrowing crate or pen by day 110 — this gives her 4 days to settle before farrowing. Wash the sow with mild soap before moving. Reduce feed to 50% from day 110 to prevent post-farrowing constipation and MMA syndrome.
How important is colostrum for piglets?
Colostrum is CRITICAL — piglets are born with no immune protection. They must receive colostrum within 6 hours of birth for maximum antibody (IgG) absorption. The piglet's gut closes to large protein absorption within 24-36 hours. Piglets without adequate colostrum have 50%+ mortality rates.
Why do piglets need iron injections?
Piglets are born with iron stores for only 3-5 days, and sow's milk contains almost no iron. Without supplementation, piglets develop iron-deficiency anemia by day 7-10 (pale skin, weakness, poor growth). An iron dextran injection (200mg) at day 1-3 of life prevents this.
How soon can a sow be rebred after farrowing?
Sows typically come into heat 3-7 days after weaning (not after farrowing). Most operations wean at 21-28 days, then breed on the post-weaning heat. This allows 2.3-2.5 litters per year. Breeding on lactational estrus is possible but not recommended (lower fertility).
How can I tell if a sow is pregnant?
The most reliable method is real-time ultrasound from about day 25-30, which detects fluid-filled embryonic sacs. Earlier signs include the sow not returning to heat 18-24 days after breeding (a heat-check with a boar is standard), a gradually filling udder line, and steady weight gain. Some farms use Doppler or blood/urine tests as supplements to ultrasound.
What is MMA in sows and how do I prevent it?
MMA stands for Mastitis-Metritis-Agalactia — a post-farrowing syndrome where the sow develops udder inflammation, uterine infection, and little or no milk, endangering the whole litter. Prevent it by reducing feed to about 50% from day 110, adding fiber (bran, beet pulp), ensuring unlimited clean water, keeping the farrowing area hygienic, and watching for fever, hard udders, or disinterest in piglets in the first 48 hours.
When should I do a pregnancy check on the sow?
Confirm pregnancy by ultrasound at day 25-30, when embryonic vesicles are clearly detectable. Many farms also do a boar heat-check around day 18-24 — a sow that stands for the boar is likely not pregnant and can be rebred immediately. Early confirmation lets you re-breed open (non-pregnant) sows without losing a full cycle.