Here is a Goat Gestation calculator. Very easy to use, it figures on 150 days, but remember that delivery is normal between 148 to 152 days.
You can also use in reverse to figure bred date. Enter date the doe gave birth in the Due Date box and it will figure bred date.
Here is a Sow Gestation calculator. Pigs gestation runs 3 months, 3 weeks, and 3 days. An average of about 115 days.