Swine Gestation Calculator - Pig Farrowing Date | LazyTools

Swine Gestation Calculator

Calculate your sow's farrowing date instantly using the famous 3 months, 3 weeks, 3 days rule — enter the breeding date and get the expected farrowing date, gestational stage and full pig pregnancy timeline.

114-day gestation (3-3-3) Farrowing date Piglet development stages Farrowing crate guide

Swine (Pig) Gestation Calculator Tool

Enter breeding date

Date of mating / breeding (required)

Gestation adjustment (days)

Reset

Normal gestation range: 111–117 days.
Average: 114 days (3-3-3).
Commercial lines (Large White, Landrace, Duroc cross) consistently farrow at 114 days. Heritage breeds may vary 112–117 days. Gilts (first-time sows) often farrow 1–2 days earlier than mature sows.

Enter the mating date and click Calculate

Expected farrowing date

Days elapsed

Days remaining

Gestation length

Used for this calculation

Expected litter

10–12 piglets average (range 8–20)

Typical for swine (pig)

Pregnancy progress

Gestational stage

Fertilisation & Implantation

Days 0–18

Eggs fertilised; embryos travel to uterus and implant. Critical early phase.

Organogenesis

Days 19–35

All piglet organs form. Embryos highly susceptible to nutritional stress.

Fetal Development

Days 36–75

Piglets grow rapidly; sex distinguishable. Gilt's abdomen enlarges.

Rapid Growth Phase

Days 76–100

Major weight gain. Sow's feed requirements increase significantly.

Pre-Farrowing

Days 101–114

Udder development, nesting, milk let-down signal imminent farrowing.

Looking for another animal gestation calculator?

LazyTools has free gestation calculators for 10 animals. Try the Cow Gestation Calculator next.

Cow Gestation Calculator →

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Features

Why use this free swine (pig) gestation calculator?

This tool does more than just calculate a due date — it gives you the complete gestational stage breakdown, current development notes and care timeline that most other tools leave out.

📅

Accurate due date calculation

Enter the mating date and get the expected farrowing date based on the 114-day average gestation, with early and late estimate options.

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Gestational stage with progress bar

See exactly which of the 5 gestational stages your animal is currently in, with a visual progress bar showing how far through the pregnancy you are.

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Days elapsed and remaining

Know exactly how many days have passed since mating and how many days remain until the expected farrowing date.

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Breed adjustment option

Choose early (111 days), average (114 days) or late (117 days) gestation to account for breed variation and individual differences.

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Signs and symptoms guide

Full checklist of pregnancy signs and pre-farrowing indicators so you know what to watch for at every stage.

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100% free and browser-based

No registration, no app download, no personal data collected. Works on desktop, tablet and mobile. Results instantly in your browser.

How to use

How to calculate your swine (pig)'s due date

Enter the mating or breeding date

Select the date the mating took place using the date picker. If mating occurred over multiple days, use the first confirmed mating date for the earliest estimate or the last date for the latest.

Select the gestation adjustment

Choose from average (114 days), early estimate (111 days), or late estimate (117 days) to account for breed or individual variation. The average is the best starting point.

Click Calculate Due Date

The calculator instantly shows the expected farrowing date, days elapsed, days remaining, pregnancy progress bar and the current gestational stage with development notes.

Monitor the pregnancy signs

Use the signs and symptoms section below to know what to watch for as the pregnancy progresses and begin your pre-farrowing preparations in the final stage.

Reference

Swine (Pig) gestation timeline — stage by stage

Period	Stage	Key events & signs
Days 0–18	Fertilisation & implantation	Critical embryo loss risk period
Days 19–35	Organogenesis	All organs forming; avoid stress
Days 36–60	Fetal development	Sex distinguishable; rapid growth
Days 61–75	Continued growth	Body condition maintenance
Days 76–100	Rapid growth	Increase feed; 70% birth weight gained
Days 101–110	Pre-farrowing prep	Move to farrowing crate at day 110
Days 111–117	Farrowing window	Average 114 days (3-3-3 rule)

Signs of farrowing approaching:

Udder development 2–3 weeks before farrowing
Nesting behaviour 24–48 h before
Milk let-down 12–24 h before farrowing
Restlessness and rooting
Vulva swelling
Temperature rise then drop to 38.0°C

Pre-farrowing care checklist:

Move to farrowing crate or pen at day 110
Reduce feed 2–3 days before farrowing to prevent constipation
Increase fibre (bran or sugar beet pulp)
Heat lamp at 32–34°C for piglets
Iodine for navel dipping
Iron injection for piglets at 3 days

vs the competition

How this swine (pig) gestation calculator compares

Most free swine (pig) pregnancy calculators show only a due date. LazyTools provides the gestational stage breakdown, development notes and care checklist that make this a genuinely useful tool.

Feature	LazyTools	Pig333.com	The Pig Site	National Hog Farmer
Shows farrowing due date	✓	✓	✓	✓
3-3-3 rule explanation	✓	✗	✗	✗
Stage-by-stage breakdown	✓	✗	Partial	✗
Farrowing crate setup guide	✓	✗	✗	✗
Gilt vs sow differences	✓	✗	✗	✗
Piglet care checklist	✓	✗	✗	✗

Complete guide

Swine (Pig) Gestation Period: Complete Guide

How long is a pig pregnant? The 3-3-3 gestation rule explained

See the interactive calculator above for a personalised swine (pig) gestation timeline based on your specific breeding date. The information below provides the complete background on swine (pig) pregnancy.

Pig pregnancy stages: organogenesis, fetal development and pre-farrowing

How to calculate your sow's farrowing date

Swine gestation by breed: commercial, heritage and gilt differences

Signs a sow is about to farrow: what to watch for

Setting up the farrowing crate: heat lamps, iron and colostrum

Managing gilt pregnancies: first-time sow differences

The swine (pig) gestation period averages 114 days, with a normal range of 111 to 117 days. Use the interactive swine (pig) gestation calculator above to calculate the expected farrowing date from any mating date. The tool also shows you the current gestational stage, development milestones, and days remaining in the pregnancy.

Frequently asked questions about swine (pig) gestation

How long is a pig pregnant?

Pigs are pregnant for an average of 114 days, famously described as "3 months, 3 weeks and 3 days." The normal range is 111 to 117 days.

What is the 3-3-3 rule for pig gestation?

The 3-3-3 rule is a common memory aid for the average pig gestation period: 3 months + 3 weeks + 3 days = 114 days. This makes the sow's expected farrowing date easy to calculate in the field without a calculator.

What is the swine gestation period?

The pig (swine) gestation period averages 114 days with a normal range of 111 to 117 days. Commercial breeds are highly consistent at 114 days. Gilts (first-time mothers) often farrow 1-2 days early.

How many piglets does a sow have?

The average litter is 10-12 piglets, though modern high-prolificacy sow lines can consistently produce 14-16 piglets per litter. The range is 8-20. Total born includes both live piglets and stillborn.

When should I move a sow to the farrowing crate?

Move the sow to the farrowing crate at approximately day 110 of gestation (4 days before the expected farrowing date). This gives her time to settle and reduces farrowing complications.

What is a gilt?

A gilt is a young female pig that has not yet given birth. A gilt's first litter is typically smaller than subsequent litters (5-9 piglets). After farrowing, she is referred to as a sow.

What does milk let-down mean in pigs?

Milk let-down (milk drop) occurs 12-24 hours before farrowing when the sow's mammary glands begin actively secreting milk. You can check by gently squeezing a teat - if milk streams out, farrowing is imminent.

How do I calculate pig farrowing date?

To calculate a pig farrowing date, add 114 days to the breeding date. Alternatively, use the 3-3-3 shortcut: add 3 months, 3 weeks and 3 days to the service date. This calculator does this automatically.

What temperature should a piglet heat lamp be set to?

Set the piglet heat lamp to maintain 32-34°C (90-93°F) at piglet level for the first week, reducing to 28-30°C by week 2 and 24-26°C by week 3. The sow area should be kept at 18-20°C to avoid heat stress in the sow.

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