Swine Gestation Calculator - Farrowing Date by Parity

The swine gestation calculator is a free animal-science planning tool that maps a single recorded breeding date to the expected farrowing date for a commercial white line, a heritage breed, or a mini pig, then adds a 2-day farrowing window, a heat-return check, an ultrasound pregnancy check, the embryo-attachment milestone, the preweaning vaccination start, and the prostaglandin induction window.

• • Commercial sow herd farrowing planning: Pick the breeding date and the parity of the dam to see the farrowing date, the early and late farrowing window, and the gilt-versus-sow offset for each sow on the breeding card.
• • Mini pig and pet-pig litter planning: Use the mini pig sire line to lock the 114-day farrowing date for a pot-bellied or pet mini pig so the farrowing kit is ready about 3 months 3 weeks 3 days after the recorded breeding date.
• • Gilt development and gilt-versus-sow comparison: Run the same breeding date through the gilt selector and the mature-sow selector to see the 1-day gilt offset side by side.
• • Veterinary scheduling: Pull the heat-return, ultrasound, and prostaglandin induction windows for the whole herd on a single spreadsheet.

For the bovine counterpart on the same breeding-date-to-due-date pattern, Cow Gestation Calculator maps a service date to a calving date plus the dry-off, close-up, and pregnancy-check milestones for Holstein, Angus, Jersey, Hereford, Charolais, Simmental, and Brahman cattle.

The calculator reads the breeding date, the sire line, the parity of the sow, the expected litter size, and today's date, applies the published line-specific gestation length plus the gilt parity offset and the large-litter offset, and returns the primary farrowing date, an early and late farrowing date from the 4-day window, the heat-return check, the ultrasound pregnancy check, the embryo-attachment milestone, the preweaning vaccination start, and the prostaglandin induction window.

• Sire line: Commercial white line 114 days, heritage breed 115 days, mini pig 114 days. The 1-day shift between heritage breeds and modern commercial hybrids is baked into the per-line baseline.
• Parity and litter size: Gilts add +1 day, second-parity and mature sows add 0 day, and large litters subtract 1 day because uterine distension can trigger parturition earlier.
• Breeding date: Service date or artificial insemination date, day 0 of gestation.

The 2-day early-and-late farrowing window brackets the within-sow variation around the computed farrowing date for the chosen line, parity, and litter size, not the broader 109 to 120 day population range.

According to Merck Veterinary Manual - Breeding Management of Pigs, the average swine gestation is 115 plus or minus 2 days and is somewhat shortened in sows with large litters, with real-time B-mode ultrasonography most accurate between day 24 and day 30 post-breeding and prostaglandin F2-alpha induction at day 113 to 114 producing farrowing 18 to 36 hours later in 80 to 90 percent of sows.

A 147-day ovine gestation is a much longer cycle than a 114-day porcine one, and Sheep Gestation Calculator returns the lambing date plus the flushing, scanning, and lambing-shed milestones for a ewe on the same form.

Four ideas carry most of the meaning behind the farrowing date, the 4-day window, and the milestone readouts.

Once the farrowing date and the preweaning vaccination start are set, the next metric to track is piglet survival, and Animal Mortality Rate Calculator returns the stillbirth and preweaning mortality rates that pair with the Merck 5 to 10 percent stillbirth benchmark for the same litter.

Treat the calculator as the day-of-service-to-farrowing record for a single sow or gilt. The breeding date, the sire line, the parity, the expected litter size, and today's date are the five inputs, and the farrowing date plus the milestone windows come out the other side.

1. 1 Enter the breeding date: Use the service date or artificial insemination date as day 0 of gestation. The calculator accepts a date from 1900-01-01 to 2100-12-31 and reports a validation message if the field is left blank.
2. 2 Pick the sire line: Choose commercial white line (114 days), heritage breed (115 days), or mini pig (114 days). The published average is shown in the option label.
3. 3 Pick the parity of the dam and the expected litter size: Use gilt, second-parity sow, or mature sow for the parity, and small, average, or large for the litter size. The two offsets are additive on top of the per-line baseline.
4. 4 Read the farrowing date and the 2-day farrowing window: The result panel shows the primary farrowing date, the early farrowing date 2 days before, and the late farrowing date 2 days after.
5. 5 Read the five milestone windows: The result panel shows the heat-return check, ultrasound pregnancy-check, embryo-attachment, preweaning vaccination start, and prostaglandin induction windows.
6. 6 Track the days-pregnant and the percent progress: The days-pregnant and gestation progress values update from today's date. The progress caps at 100 percent once the breeding date is past the expected farrowing date.

Example: a registered Yorkshire gilt was AI-bred on 2026-05-16 with an expected average litter. The calculator returns a 115-day farrowing on 2026-09-08, a 2-day early-and-late farrowing window from 2026-09-06 to 2026-09-10, and a prostaglandin induction window from 2026-09-07 to 2026-09-08.

A 63-day canine gestation is a much shorter cycle than a 114-day porcine one, and Dog Pregnancy Calculator handles the same breeding-date-to-due-date pattern for a small-herd or backyard setting that complements the swine gestation math.

A calculator that follows the published line table turns a single breeding date into the farrowing date, the 2-day farrowing window, and the milestone windows a producer, heritage breeder, or pet mini pig owner needs to plan the calendar.

• • All three sire-line baselines on one form: Commercial white line, heritage breed, and mini pig are pre-loaded, so the same breeding date can be re-read for each line without manual math.
• • Surfaces the gilt parity offset and the large-litter offset: Returns the +1 day gilt offset, the 0-day second-parity and mature-sow offsets, and the -1 day large-litter offset alongside the line baseline.
• • 2-day farrowing window: Returns the primary farrowing date plus an early and late farrowing date 2 days in each direction, so the farrowing crate slot can be planned against the within-sow variation around the line, parity, and litter-size average. The broader 109 to 120 day range is a population reference.
• • Five milestone windows in one read: Pairs the farrowing date with the heat-return check, the ultrasound pregnancy check, the embryo-attachment milestone, the preweaning vaccination start, and the prostaglandin induction window.

Four variables change the farrowing date, the farrowing window, and the milestone readouts, and the calculator surfaces the most important ones in the form and the result panel.

• • The line table covers commercial white line, heritage breed, and mini pig. Cross-bred sows fall between the published line averages.
• • The gilt and large-litter offsets are each about 1 day, so the calculator is not a substitute for a breeding card on individual sows and gilts.
• • The 2-day farrowing window brackets the within-sow variation around the computed farrowing date, not the broader 109 to 120 day population range. A small share of farrowings can land a few days outside the +/-2 day band because of season, nutrition, or stress.

According to Omni Calculator - Swine Gestation Calculator, the swine gestation period is about 114 days on average and runs from 112 to 120 days depending on the sow's genetics, age, environment, nutrition, weight, and parity, with a farrowing before day 109 considered abortion and a farrowing between day 109 and day 112 considered premature.

According to Merck Veterinary Manual - Breeding Management of Pigs, embryos are at greatest risk of dying during the first 30 days of pregnancy and efforts should be directed toward avoiding stresses to the sow such as overfeeding, heat, handling or moving, and immunization during this critical period.

For the small-ruminant counterpart on the same breeding-date pattern, Goat Gestation Calculator maps a service date to a kidding date plus the dry-off, vaccination, and kidding-pen milestones for a doe on the same form.