For some, it's never enough. But a good gauge would be something along the lines of this..

• 1 x 250g - perfect for a cup each day (even weekends!), for two weeks.
• 2 x 250g - two weeks worth for a couple who like to start each day with a fresh brew.
• 1 x 1kg - for a household, a small shared studio space or office of 4 - 5 people or a really motivated individual game enough for 3+ coffees a day, for two weeks.