Simple exercises to improve piano hand independence

1. How can I improve my hand independence?
2. How long does it take to get hand independence?

How can I improve my hand independence?

Here's a way to help yourself:

1. Learn the left hand first, followed by the right hand.
2. After sufficiently learning each hand individually, combine the two hands.
3. The key thing to remember here is to take your time.
4. Gradually raise the tempo from a slow enough pace (one in which you can play the part correctly).

How long does it take to get hand independence?

If youre ONLY practicing hand independence I would say a month or two to see some real improvement. Probably closer to 3 or 4 if you're practicing other things. Don't rush it, just practice and it will come.