What Is the Swine Gestation Calculator?
The Swine Gestation Calculator estimates the farrowing (birthing) date for a sow or gilt based on her breeding date. The average gestation period for pigs is about 114 days — easily remembered by the rule of thumb "3 months, 3 weeks, and 3 days." Most sows farrow between 111 and 116 days, so this tool lets you adjust the gestation length to match your herd's history.
How to Use It
Enter the date the sow was bred (or artificially inseminated) and the expected gestation length in days. The default of 114 days reflects the breed-average for domestic pigs. Click calculate to see the predicted farrowing date along with a breakdown of the day, month, and year.
The Formula Explained
The calculation simply adds the gestation period to the breeding date:
$$\text{Due Date} = \text{Breeding Date} + 114 \text{ days}$$
Calendar math handles month lengths and leap years automatically, so you always get an accurate target date.
Worked Example
Suppose a sow is bred on January 1, 2024. Adding 114 days lands on April 24, 2024. January contributes 30 remaining days, February (a leap year) adds 29, March adds 31, leaving 24 days into April — $$30 + 29 + 31 + 24 = 114.$$ So the expected farrowing date is April 24, 2024.
FAQ
How long are pigs pregnant? The average swine gestation is 114 days (about 3 months, 3 weeks, and 3 days), with a normal range of roughly 111–116 days.
Why can I change the gestation length? Gestation varies slightly by breed, litter size, and individual sow. Adjusting the days lets you fine-tune the prediction based on your own records.
Is the due date exact? No — it is an estimate. Monitor the sow closely as the date approaches and prepare the farrowing area a few days early.
