พอดีอ่านเจอเลยเอามา ฝาก

Equivalents  
1 cup buttermilk   =  1 cup yogurt
1 cup buttermilk   =  1 cup milk PLUS 1 Tbsp vinegar or lemon juice (let stand for 10 minutes before using in recipe)
1 cup buttermilk   =  1 cup milk PLUS 1-3/4 teaspoons cream of tartar
1 cup buttermilk   =  1 cup water PLUS 4 Tbsp powdered buttermilk (reconstitute before using or add dry to dry ingredients and wet to wet ingredients before mixing
1 cup buttermilk   =  1/4 cup milk PLUS 3/4 cup yogurt
1 cup buttermilk   =  8.5 ounces
1 cup buttermilk   =  242 grams

http://homecooking.about.com/library/weekly/aa012901b.htm