You should adjust the amount of coffee to water based on taste preference. The grind and brew method will also impact flavor. This makes it difficult to say exactly how many cups a bag will brew.
If you follow the suggested recommendation and use 2 tablespoons of coffee to 6 ounces of water, a 12-ounce bag of coffee will yield approximately 32 cups of coffee, and a 16-ounce bag of coffee will yield approximately 42 cups of coffee.