One cup of cucumbers (with the peel) has about: 1  16 calories. 2  Zero protein, fat, fiber or sugar. 3  17 milligrams vitamin K (22 percent DV)  3 milligrams vitamin C (4 percent 1  DV) 6 milligrams magnesium (4 percent 2  DV) 152 milligrams potassium (4 percent  DV) 8 milligrams manganese (4 percent DV)