You need around 7 – 8 hours sleep per night.
Less than that and you’re functioning as well as if you were drunk, and you lose the ability to judge how functional you are (I don’t feel tired!). More than that can also be bad for your health
If you’re wanting to improve your own performance, then making sure you have at least 7- 8 hours each night will go a long way to getting you there.
And here’s a tip on how to get to sleep more quickly.