The general guideline for brewing coffee is to use approximately 1 to 2 tablespoons of coffee grounds per 6 ounces of water. Since a standard cup of coffee is typically 6 ounces, you would need about 2 tablespoons of coffee grounds for each cup.
For 12 cups of coffee, you would multiply the number of cups by the amount of coffee grounds per cup. In this case, it would be:
12 cups x 2 tablespoons = 24 tablespoons