Swine gestation timeline and expected farrowing date calculator
Swine Gestation Calculator
This calculator helps you estimate the expected farrowing date for a sow based on the breeding (or insemination) date. It also creates a practical milestone timeline and a configurable farrowing window to support planning and routine checks.
How the calculation works
The core estimate is the expected farrowing date:
\( \text{Due Date} = \text{Breeding Date} + \text{Gestation Length (days)} \)
Many farms reference the rule of thumb 114 days (often described as “3 months, 3 weeks, 3 days”), but real-world variation exists. To model that uncertainty, the calculator uses a user-selected window:
\( \text{Earliest} = \text{Due Date} - \text{Window} \)
\( \text{Latest} = \text{Due Date} + \text{Window} \)
Progress and timing
To show “where you are” in the pregnancy, the calculator compares your chosen Reference date to the breeding date:
\[ \text{Elapsed Days} = \max(0, \text{Reference Date} - \text{Breeding Date}) \] \[ \text{Progress \%} = \frac{\text{Elapsed Days}}{\text{Gestation Length}} \times 100 \]
If the reference date is beyond the latest farrowing window, the table highlights the farrowing milestone to signal that your inputs may need review.
Milestone timeline table
The table includes a set of practical milestones such as pregnancy check, vaccination reminders, and moving the sow to a farrowing pen. In Advanced view, you can customize the day-based timing of these milestones to match your workflow, while keeping the due-date math consistent.
Use responsibly
This calculator is intended for planning and education. Health, parity, genetics, management practices, and environmental conditions can influence outcomes. If you suspect a problem or an unusual delay, consult a qualified veterinarian.