Gestation Period (Animals) Calculator

Work out gestation period (animals) instantly with clear inputs, formula shown and shareable results.

About Gestation Period (Animals) Calculator

Adds the species-typical gestation length to the breeding date and shows a one-week window either side.

Formula

Gestation lengths

Cow 283 days, mare 340, sow 114, ewe 147, goat 150, dog 63, cat 65, measured from service or ovulation

Worked example

With the default values below, Gestation Period (Animals) Calculator returns Expected due date of June 11, 2027. Change any input above and every figure here is recalculated in your browser.

Inputs used

Speciesone of Cow (283 days), Mare (340 days), Sow (114 days), Ewe (147 days), Doe goat (150 days), Dog (63 days), Cat (65 days): Cow (283 days)
Breeding date: 2026-09-01

Results

Expected due date: June 11, 2027
Gestation length: 283 days
Earliest expected: June 4, 2027
Latest expected: June 18, 2027

Step by step

1Values used
2Gestation lengths
3Expected due date= 2027-06-11
4Gestation length= 283 days
5Earliest expected= 2027-06-04
6Latest expected= 2027-06-18

Assumptions and limits

The result is derived only from the 2 inputs listed above. Anything not among them is not part of the calculation.
In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
Figures are rounded for display to whole numbers, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Frequently Asked Questions

How variable is gestation?

Usually within a few days for pigs and dogs, but mares commonly vary by two to three weeks.

Does litter size matter?

Yes. Large litters tend to shorten gestation slightly in pigs and dogs.