what animal has the biggest brain

The sperm whale has the biggest brain of any animal species, weighing up to 20 pounds (7 to 9 kilograms) . The mature adult sperm whales brain weighs an average of 18 pounds, and can grow to be nearly 500 cubic inches in size. The sperm whale's head comprises 25 to 35 percent of its entire body length. However, it is important to note that brain size is not always a perfect predictor of animal intelligence.