How much practicing does one really need?

How long is a piece of string?

Depends on how good you are, how good you want to be and how quickly you want to get there.

An absolute beginner will probably still improve on 10 minutes a day.
A music student aiming to be a world class concert pianist 4 hours a day (??? not really sure but a lot more than 10 minutes! )

I never did more than an hour a day, even when I was practising for ALCM.
Whe I was doing Grade 8 organ I only had access to an organ on two days a week, and then only did an hour a day

It really depends..

If you are very awake and alert, 2-3 hours,
if your half asleep, then I wouldnt even encourage practising, going over a couple of known pieces to keep your fingers going is wise. ~ ( other factors are fatigue and muscle stress/development. )

If im learning a new piece of music I will spend maybe 1-2hours learning it a night until I have learnt it,
but once ive learnt it the time is normally halved, most of this time is spent on developing weaker areas, ~ Only playing through the whole piece 1-2 a week, listening for weaknesses and to keep the piece in good form.

When your tired of a piece, switch it, there's no point practising if you have no energy left for it, ~ practice time can be waisted when you could play something totally different, another section of the piece etc.

So practice time, be alert, know what your doing, know when to stop.
If you dont you may find practising causes mistakes, which needs more practising to be overcome.

I was told a story once, my aunty said to a teacher.. practice makes perfect... he responded, perfect practice makes perfect.

Of course the answer is "it depends".

But for me, I find that half an hour of very focused practice, concentrating hard on the specific areas to which my teacher has guided me, is significantly more worthwhile than a couple of hours of bumming around playing "stuff". But I still do the latter from time to time because it's fun!

Incidentally the above applies to the piano. I also play the horn, for which it is worthwhile to play any old piece each day to retain my physical stamina.

Jon

I'm at a Conservatoire and they expect a minimum of four hours a day. But it all all depends on HOW you practice. If you're not completely focused, you don't achieve anything and can easily waste a lot of time messing around half heartedly.

A lot of people at my college are in at 9am and put in about 6 hours a day, but I think that is way too much. If you're focused you'll probably do with half of that.

Before I came to college I done about an hour or two a day. I always put in an hour for scales and sightreading every morning though.

I try now to do 1 hour per day. I would like to do much more but I am so busy at the moment that it isn't attainable.

I think doing only one hour makes me think more about what I am doing so maybe it is more effective!

I think the OP knew that it is a very silly question.