# Swine Gestation Calculator

Calculate your sow's expected farrowing date from the breeding date. Covers Yorkshire, Duroc, Hampshire, Berkshire, Landrace, and other pig breeds.

## What this calculates

The old farmer's rule for pig gestation is '3 months, 3 weeks, and 3 days,' which works out to about 114 days. Enter the breeding date and breed to calculate the expected farrowing date and prepare your farrowing facilities on time.

## Inputs

- **Breeding Month** — options: January, February, March, April, May, June, July, August, September, October, November, December
- **Breeding Day** — min 1, max 31
- **Breeding Year** — min 2020, max 2040
- **Pig Breed** — options: Average (114 days), Yorkshire/Large White (113 days), Duroc (114 days), Hampshire (114 days), Berkshire (115 days), Landrace (115 days), Meishan (116 days), Chester White (113 days)

## Outputs

- **Expected Farrowing Date** — formatted as text — Predicted farrowing date based on breed average gestation
- **Earliest Likely Date** — formatted as text — Earliest expected farrowing (gestation - 3 days)
- **Latest Likely Date** — formatted as text — Latest expected farrowing (gestation + 3 days)
- **Average Gestation Length** — Average gestation period for selected breed
- **Days Until Due Date** — Days remaining from today until expected farrowing
- **Current Gestation Week** — formatted as text — How far along the pregnancy is today

## Details

Swine gestation is remarkably consistent across breeds, averaging 114 days (about 3 months and 24 days). The variation between breeds is only 2-3 days, making farrowing one of the more predictable events on a livestock operation.

**Breed-specific averages:**

- **Yorkshire/Large White:** 113 days
- **Chester White:** 113 days
- **Duroc:** 114 days
- **Hampshire:** 114 days
- **Berkshire:** 115 days
- **Landrace:** 115 days
- **Meishan:** 116 days

**Factors that affect farrowing date:**

- **Litter size:** Sows carrying larger litters tend to farrow 1-2 days earlier
- **Parity:** First-litter gilts may farrow a day earlier than experienced sows
- **Season:** Some research shows slightly shorter gestations in summer
- **Induction:** Many commercial operations induce farrowing with prostaglandin (Lutalyse) on day 113 to synchronize births for management purposes

**Preparing the farrowing area:**

Move the sow to a clean, disinfected farrowing crate or pen about 5-7 days before the expected date. The area should be warm (heat lamps set at 90-95F for piglets), dry, and draft-free. Have towels, iodine for navel dipping, and a source of supplemental colostrum on hand. Most sows farrow without assistance, but monitoring the first few hours is important to make sure all piglets find the teats and start nursing.

Sows typically deliver their entire litter over 2-5 hours, with 15-20 minutes between piglets. If more than 45 minutes pass between piglets, intervention may be needed.

## Frequently Asked Questions

**Q: How long are pigs pregnant?**

A: Pigs are pregnant for approximately 114 days, which is commonly remembered as '3 months, 3 weeks, and 3 days.' This is one of the most consistent gestation lengths among livestock, with most sows farrowing within 2-3 days of the average. Individual variation from 111 to 117 days is considered normal.

**Q: How can I tell when a sow is about to farrow?**

A: In the last 24-48 hours before farrowing, watch for: restlessness and nesting behavior (rooting at bedding), milk letdown (you can express milk from the teats), swelling of the vulva, increased respiratory rate, and a slight drop in body temperature. Some sows stop eating 12-24 hours before farrowing. The udder will feel full and tight.

**Q: How many piglets does a sow have?**

A: Average litter size varies by breed and parity. First-litter gilts typically have 8-10 piglets. Experienced sows average 10-14 piglets, with some producing 16+. Prolific breeds like Meishan or modern genetic lines selected for litter size can average 14-18 born. Not all piglets born alive will survive to weaning, and overlaying by the sow is the most common cause of pre-weaning mortality.

**Q: When can a sow be bred again after farrowing?**

A: Sows typically come back into heat (estrus) 3-7 days after piglets are weaned. In commercial operations that wean at 21-28 days, this means the sow can be rebred about 25-35 days after farrowing. This allows approximately 2.2-2.5 litters per sow per year. Breeding at the first post-weaning heat generally results in good conception rates.

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Source: https://vastcalc.com/calculators/health/swine-gestation
Category: Health & Fitness
Last updated: 2026-04-08