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How much RAM is enough?

Vjosullivan

macrumors 6502a
Original poster
Oct 21, 2013
994
1,157
I recently purchased a well spec'd iMac with 8GB of RAM, on the basis that I would buy 3rd party RAM when I found that I needed it... I need it.

Most things run fine but I've finally come across a situation where I need more RAM. In my case it is using Adobe Lightroom to stitch together multiple large (50MB) pictures into a panorama. The activity monitor shows over 7GB of RAM in use and the process is very, very slow.

So, having established that I do need more RAM, the next question is how much? Is there any way of determining how much RAM the computer would use to perform a given task if it had more than enough?

I don't want to get another 32GB of RAM only to find I should have gotten 64GB (or vice versa).
 

keysofanxiety

macrumors G3
Nov 23, 2011
9,534
25,267
So, having established that I do need more RAM, the next question is how much? Is there any way of determining how much RAM the computer would use to perform a given task if it had more than enough?

macOS uses as much RAM as you can throw at it. That said, there's only so much RAM it can practically use depending on what the application is throwing at the system.

I'd say for your usage, 32GB is the sweet spot between large enough for comfort & futureproofing but without being overly excessive (64GB). You'd be really really hard pressed to use more than 32GB RAM.
 
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vertical smile

macrumors 603
Sep 23, 2014
5,325
6,186
Is this a 27” iMac?

I think 8GB is low, unless doing very basic stuff.

24GB would be cheap to get to, and would probably be good for your needs.

To keep upgrade costs down, you could just go with a 16GB kit containing two 8GB sticks. That would give you 24GB, and you can see how that does.

If you find you are needing more RAM, then get two more 8GB or just go to two 16GB sticks for 32GB, or 48GB depending on what you go for.

You could do the above, but first get a 32GB kit (2x16GB sticks) instead of the 16GB kit. That would start you off at a very healthy 40GB of RAM, and probably more than you will ever need.

But of course, you could get another 32GB kit down the road to get you to 64GB.
 
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Ledgem

macrumors 68000
Jan 18, 2008
1,891
723
Hawaii, USA
Unfortunately there's not really a great way to know, other than possibly hearing guidance from others. Photo stitching can take up quite a bit of RAM, but I'd be surprised if you needed to go to 64 GB or beyond.

What I can offer is that I do a fair bit of photo editing and manipulation with 50 megapixel files. Granted there's no stitching, but I do fine with 32 GB of RAM. It may even be slightly overkill for me, but at least I don't run into performance issues, despite fairly heavy multitasking. So, given my own usage (which differs from yours a bit), I'd think 32 GB would work well for you and still give you some room to grow.
 
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nihil0

macrumors 6502
May 19, 2016
367
245
I use Ps and Lr (combined with Luminar 3) for photography editing and 24 GB RAM is enough for me. It never goes into yellow numbers no matter how much I push it.
 
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alien3dx

macrumors 65816
Feb 12, 2017
1,269
256
I recently purchased a well spec'd iMac with 8GB of RAM, on the basis that I would buy 3rd party RAM when I found that I needed it... I need it.

Most things run fine but I've finally come across a situation where I need more RAM. In my case it is using Adobe Lightroom to stitch together multiple large (50MB) pictures into a panorama. The activity monitor shows over 7GB of RAM in use and the process is very, very slow.

So, having established that I do need more RAM, the next question is how much? Is there any way of determining how much RAM the computer would use to perform a given task if it had more than enough?

I don't want to get another 32GB of RAM only to find I should have gotten 64GB (or vice versa).
OSX tend to compress ram if not used.. if in developer purpose, how much database size x 3 is your suppose needed ram. For normal usage mine, 8 GB is enough.But if you tend see some developer opening mutiple virtual machine and others then you may need more then 32 GB ram. I tend to see some people open browser tab more then 30 and 8 GB is beyond enough.. 16GB required. If you do multi tasking a lot just max em all the 48 maybe ? but for just average jo user just 8 GB mere enough .
 
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whosthis

macrumors member
Aug 21, 2008
89
22
The good thing with the current super fast SSDs is that swapping memory to disk is much faster than some years ago. Bad thing about it is that it is still annoying, and you don't always realize it is happening (and you don't hear the disk working).

RAM is really affordable now, even the large modules. I see no point in saving a couple dollars here and inserting a potential bottleneck in an otherwise speedy and costly computer.

Keep in mind that image stitching is a really expensive operation and typically needs your images loaded. And they are *much* bigger when loaded than compressed as jpg or png on disk.

With additional 2x16GB you should be fine. If you want to future proof and do not want to worry about the future at all, get 2x32 (which still leaves you the option for 128 GB in total without wasting those modules). 2x8 may be good enough, I don't think the little saved money is worth it, though. But if you are running base model and HDD and are on a budget, that's still a sensible choice.
 
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Vjosullivan

macrumors 6502a
Original poster
Oct 21, 2013
994
1,157
Thanks for all the advice.

10 minutes ago I installed 32GB of RAM into this machine. My very first task was to open Lightroom and have it stitch together 15 50MB pictures into a panorama. (This was the task that previously killed the machine if more than eight pictures were involved.) This time the whole process took under 20 seconds. According to the Activity Monitor, memory used peaked at around 14GB, well short of the new 40GB limit. I'm very happy with that.
 
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vertical smile

macrumors 603
Sep 23, 2014
5,325
6,186
According to the Activity Monitor, memory used peaked at around 14GB, well short of the new 40GB limit. I'm very happy with that.

I am glad it worked out for you.

24GB may have been fine for you, but with RAM pricing relatively cheaper, I probably would have done the 40GB too.
 
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nihil0

macrumors 6502
May 19, 2016
367
245
My iMac has only 8 and I used LR (not PS as much) and it was fine with 8GB ¯\_(ツ)_/¯

I edited photos on my wife's 2016 Macbook (m3, 8GB, 256 GB SSD) using same apps and I found out that 8 GB was not enough, RAM was running into red numbers
 
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Gravydog316

macrumors 6502
May 17, 2016
427
161
Canada
You can NEVER have enough RAM.
too bad you couldn't get RAM like an external hard drive, & just plug it in lol
 
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throAU

macrumors 604
Feb 13, 2012
6,851
4,519
Perth, Western Australia
How long is a piece of string?

It depends heavily on your workload, my work machine for example has 64 GB and i am regularly using 50-60 GB of RAM (not cache) for my workload.

Be aware however that a modern OS will attempt to use all the RAM you have for disk cache if it is not needed for anything else.

So just be sure to check whether or not most of your usage is cache before assuming you're out of RAM. If it's used as cache, that's good - the OS will reclaim from cache if needed.

As above, there's a price to performance sweet spot even if you don't "need" a heap and for most "normal" workloads that's about 16 GB.
 
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