Question: how much water for 1/2 cup coffee grounds?
Answer:  cup = 10 oz water + 2 1/2 tbsp coffee.  cups = 20 oz water + 5 tbsp coffee.  cups = 30 oz water + 7 1/2 tbsp coffee.  cups = 40 oz water + 10 tbsp coffee.  cups = 50 oz water + 12 1/2 tbsp coffee.