What this calculator does
Swine gestation (farrowing date) works out expected farrowing date from the breeding date, using the average 114-day sow gestation. Enter your own figures above and the answer updates as you type: nothing is fixed in the code, so the result reflects exactly the numbers you supply.
The formula this calculator evaluates is printed under the tool and explained below, so you can check the working by hand or reuse it in a spreadsheet.
The formula
The inputs explained
| Field | What to enter |
|---|---|
| Breeding date | A calendar date. |
Worked examples
Every figure in the tables below is produced by this page’s own calculator at build time, so the numbers and the tool always agree. Select any row to load that scenario.
Examples across different dates
The same calculation at a range of dates, with every other input held at its starting value. These are generated relative to the day the page was built.
| Breeding date | Expected farrowing date | Gestation length used | Days from today |
|---|---|---|---|
| 2026-08-16 | 8 Dec 2026 | 114 days | 120 |
| 2026-09-08 | 31 Dec 2026 | 114 days | 143 |
| 2026-11-07 | 1 Mar 2027 | 114 days | 203 |
| 2027-02-05 | 30 May 2027 | 114 days | 294 |
| 2027-08-09 | 1 Dec 2027 | 114 days | 478 |