I usually just use the back of some other piece of paper. I have been doing it for so long now that I can easily divide the page into seven columns, then draw lines to make a calendar for 2-3 weeks (a pay period around here. I just jot down meal ideas according to the calendar and make a shopping list from there. I once tried using an extra calendar we had, but it was a nuisance. I like using 'scrap' paper so it gets used thoroughly before it gets recycled and because it is easier to stick to the fridge than a whole calendar!