The average cat spends the majority of its day sleeping, usually an average of 15 hours a day, which is 62.5 percent of the day. However, this is not simply a product of laziness, and there is practical reason for this high percentage; cats have evolved as predators, and the need to conserve energy to allow for plenty of energy for hunting is part of that evolutionary process. Additionally, though cats may spend a lot of time laying still with their eyes closed, they are usually not in a state of deep sleep, which cats tend to experience in 5-minute bursts.
Cat owners who are concerned that their felines appear to be snoozing for most of the day may take comfort in the fact that not only is it natural for a cat to spend the majority of its day sleeping, but cats are also mostly inactive during the day. The technical term for this is crepuscular, which means that cats are at their most active at dawn and dusk, while the sun is rising and setting. Indoor pet cats are also likely to adapt their schedules to match the activity of the house they live in, meaning they may sleep more while their humans are asleep.