How much memory

How much memory do you need to run in 64bit mode is 6gb enough?

I run Windows 7 64 bit and SONAR 32 bit (mainly, although use 64 bit sometimes) with a "mere" 4GB.  Absolutely fine.

6 GB is probably enough for most people.

There's a heck of a lot more than just "Windows" going on, that's only a generic term.
Charly is right here, environmentally around 3Gb is generally taken up straight away before you do anything. Then memory starts swapping to hard drive if you don't have enough of it.
 
Well anyway ... you can find out yourself...
https://technet.microsoft.com/en-gb/sysinternals/bb896653.aspx
 
In my view pretty much every PC (whatever the requirement) should really have 8Gb minimum installed nowadays. Double it for DAW's.

I used to run Win 7 x64 with Sonar x64 on 8GB which was totally fine for most applications, even 50+ tracks of heavy mixing with Steven Slate VCC etc.

When I started doing large-scale composing for TV I got frustrated with popping and latency when there are a bunch of synths open, and now I run 24GB. I don't think the indicator has ever showed more than 8GB in use, but I can keep 30 - 40 synths live with samples loaded and still get killer performance plus no latency.
 
My PC is only an i7 2600 (about 4 years old) with 1333 DDR3 RAM so I'm sure those numbers can improve tremendously by now, esp with faster bus speeds.
HOWEVER, the quality of your soundcard drivers may well make a huge difference too. I'm spoilt with RME :O)

LJB
My PC is only an i7 2600 (about 4 years old) with 1333 DDR3 RAM so I'm sure those numbers can improve tremendously by now, esp with faster bus speeds.

I run similar spec's. I still can't believe how well it runs under my DAW environment.
 

LJB
HOWEVER, the quality of your soundcard drivers may well make a huge difference too.

 
Absolutely agree..

Best Practice for Mac.....fill 'er up/max it out
Best Practice for PC......try to add at least 4gb to a stock PC if you have the slots.
 
Any rendering of audio or video needs anything it can get. 6(minimum)-8-12 will git-r-done. I had 2 4gb sticks so I just got 2 more..

charlyg
Best Practice for Mac.....fill 'er up/max it out
Best Practice for PC......try to add at least 4gb to a stock PC if you have the slots.

 
Macs and PC's run on similar hardware so not understanding why the different advice.

Macs use ram from top down. Microsoft has always been bottom up. Going to Intel and/or 64 bit may have changed things. I retired a few years ago....

bitflipper
The only way to know if you have enough RAM is to check usage on a large project. If you've got memory remaining in reserve, and you're not seeing excessive page faults, then you're set.

Yep... 
As long as you have enough RAM for your most dense projects, adding more will not increase performance.
16GB is plenty for many users.
More extreme Vi users may need 32GB or even 64GB.
 
For dual-channel motherboards:
If you want/need 16GB, use two 8GB sticks... which leaves the option to move to 32GB without throwing away existing RAM.  If you add RAM, make sure to install identical sticks (this eliminates potential RAM compatibility issues).
 
For quad-channel motherboards:
If you're running a quad-channel motherboard, you're probably more concerned about performance than cost.
Go with four 8GB sticks (32GB total)... which leaves the option of moving to 64GB without throwing away existing RAM.

16G allows plenty of space for softsynth samples for me.  I am quite sure I would be hitting a wall if I had less than 8G.  My piano alone needs 1.5G.  Windows and background tasks use almost 3G on my machine.

Make sure the RAM you buy is matched to what you already have.
 
Better still, buy a new stick(s)

What hockeyjx said.
 
Also, adding a SSD for (at a minimum) the system drive, with samples on a separate drive, would go a LONG way towards improving performance on most modern machines!
 
FWIW...

As others have said, it just depends on what you're going to be doing in Sonar. I use Sonar for composing video game music, and I work 99% with sample libraries and synths, so I use up a lot of RAM on heavily populated projects. I was getting by with 12GB for a while, but when I started writing more complex orchestral compositions, even 12GB wasn't enough. I had to upgrade to 16GB. If you're planning on using a lot of high quality/high resource sample libraries simultaneously, you'll be better off with a lot more than 6GB :)