From Dunkin Donuts website:
Dunkin' Donuts Iced Coffee
Make your own delicious Dunkin' Donuts Iced Coffee! Buy Dunkin' Donuts coffee beans online now and then follow these simple steps:
To brew a full-flavored pot of Dunkin' Donuts Iced Coffee, double the amount of coffee grinds you would normally brew for hot coffee*. Measure 4 level tablespoons for every 6 oz. of cold spring or filtered water you plan to brew.
After the coffee is done brewing, remove it from the burner and let cool.
Pour the coffee into a temperature safe container, and add ice until the mixture cools and doubles in volume. Keep in mind that the melting ice dilutes the coffee, which is why Iced Coffee is brewed using twice the amount of grinds at hot coffee.
To keep Iced Coffee cold and fresh, store it in an airtight container in the refrigerator. Iced Coffee should be consumed within eight hours after brewing.
Drink as is, or add milk, cream or sugar to sweeten and lighten to taste.
To keep the remaining, unbrewed Dunkin' Donuts Coffee beans or grinds fresh, store in an opaque, airtight container in a cool dry place. Do not store in a refrigerator as grinds and beans absorb moisture and aromas around them.
* Be sure not to over fill your brew basket