Pig Gestation Calculator (farrowing date: 114 days, 3 months 3 weeks 3 days)

Understanding the pig gestation calculator — concept and principle

This calculator gives a sow's expected farrowing date from the breeding date, compares it with the "3 months, 3 weeks, 3 days" rule, and shows how far along she is today and when key signs can be expected. Pig keepers use it to plan farrowing pens, feeding changes and vet visits.

3 months, 3 weeks, 3 days: with the default inputs the result is Jan 13, 2027 (expected farrowing).

How it is calculated

Expected farrowing = breeding date + 114 days.
Memory rule date = breeding date + 3 calendar months + 24 days (3 weeks and 3 days).
Days pregnant = today − breeding date; days to due = 114 − days pregnant.
Week = floor(days ÷ 7) + 1; progress = days ÷ 114.
Vet confirmation from about day 30; belly and udder may show from about day 80.

The principle

Sows are pregnant for about 114 days, often remembered as "3 months, 3 weeks and 3 days". The rule is handy but months have different lengths, so on the calendar it can land a day or two away from exactly 114 days. A vet can confirm pregnancy from about day 30, for example by ultrasound. Owners often notice the belly and udder from about day 80–90; colostrum usually appears 24–48 hours before farrowing, and the sow becomes restless and builds a nest in the last hours.

Worked example

Default inputs: bred on Sep 21, 2026, viewed on Nov 10, 2026.

Expected farrowing = Sep 21 + 114 days = Wed, Jan 13, 2027.
Memory rule: Sep 21 + 3 months = Dec 21, + 24 days = Thu, Jan 14, 2027.
Days pregnant = 50; days to due = 64; week 8; progress = 50 ÷ 114 = 44%; stage before the expected date.
Vet confirmation from Wed, Oct 21, 2026; belly and udder from Thu, Dec 10, 2026.

How to read the result

Move the sow to a clean farrowing area a few days before the date so she can settle. Watch for milk in the teats, nesting and restlessness. Keep records of each sow's actual farrowing date; it helps you plan future litters.

Common mistakes

Using the first day of heat instead of the mating date.
Expecting farrowing exactly on the date.
Moving the sow too late into the farrowing pen.
Missing a return to heat about three weeks after mating, which suggests she is not pregnant.

Keep in mind: This is an estimate, not a diagnosis. Call your vet if farrowing is well overdue, if the sow strains without piglets, or if she shows fever or loss of appetite.

Frequently asked questions

How long is a pig pregnant?

About 114 days, or 3 months, 3 weeks and 3 days.

When can I confirm a sow is pregnant?

A vet can usually confirm it from about day 30.

How do I know farrowing is near?

Milk can usually be expressed 24–48 hours before, and the sow becomes restless and nests.

Sources: Purdue University Extension VA-30-W, J. H. Koziol, "What to Expect When: Your Sow is Expecting" (2021)

Checked 9 Nov 2026. Purdue University Extension VA-30-W, J. H. Koziol, “What to Expect When: Your Sow is Expecting” (2021): 114 days (3 months, 3 weeks and 3 days), confirmation about day 30, abdominal distention from 80–90 days.

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