Borage Oil Yields

I would like to know the oil yield extracted from seeds. I mean, for each kilogram of seeds, how much oil can we obtain from extraction.

The oil content of borage seed is ca. 30-31%. So for each kilogram of seed, if your extraction method is efficient, you should recover about 300 grams of oil. In practice, the actual yield will be slightly less than this.
On a per hectare basis, seed yields are 100 kg/ha. This works out to about 30 kg oil per hectare.