Naps during the day do actually count towards your hours of sleep.
If you cannot get enough sleep during the night then taking an hour or so nap during the day can help you catch up on your sleep.
However it's best to try and get most of your sleep at night and not during the nap as napping too much can affect your sleep at night.
The perfect nap length is considered to be at least 90 minutes.
A nap of between 14 to 20 minutes is called a power nap which helps refresh you when you need a quick nap.
However if you need a longer nap to give you more energy then taking a nap of at least 60 to 90 minutes will help recharge you.