How many cups do I actually need?

Manufacturer 'cups' are typically 5 oz, not mug-sized. A '12-cup' carafe is roughly 60 oz, or about six standard 10 oz mugs. For a single drinker, an 8-10 cup machine with a 1-4 cup mode is usually plenty; for households of three or more, or office use, 12-14 cup capacity is the more common recommendation.