How much has that Mac been used?

23 January 2017, 11:30

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Knowing how much a Mac has actually been used by its owner can be very useful if you’re buying pre-owned. A Mac three years old that’s been used very infrequently could be a better purchase than a two-year old Mac that’s been left running 24/7, for example.

While physical condition of the Mac gives a clue, you can garner some further clues by a little software probing. It’s not entirely accurate, and comes with substantial caveats, but could be worth a try.

Battery charge cycles
This is obviously only of use on a MacBook (including Pro/Air), but the number of times a battery has been charged is useful information. This is represented as the charge cycle figure. A low charge cycle figure on an older Mac means one of two things: either the Mac hasn’t been used much or – and perhaps more likely – the Mac has spent most of its life attached to its charger, so might rarely have left the owner’s home or office. Either way, a low number is good news.

What’s a low number? My current MacBook Pro, which is 1.5 years old and spends half of its life on charge, and half running on battery, has a cycle count of 378. This is a healthy average figure for the age of this computer. Although it’s impossible to estimate, if I saw something like 300 cycles on a three year-old Mac then I would be very impressed. (For what it’s worth Apple considers batteries charged over 1000 times to be in need of replacement, on models sold since 2009 at any rate; earlier models had maximum cycles of 500 or 300.)

To discover this information, hold down Option (Alt on some keyboards), then click Apple > System Information. In the window that appears, click the Power heading at the left, and then look at the Cycle Count figure on the right, beneath the Health Information heading.

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Of course, if the battery has been replaced then this info won’t be all that useful – and the best way to find out if it has is to ask the seller. However, on modern MacBook (Pro/Air) models it’s not trivial to replace the battery, so it’s less likely to have happened compared to older Macs.

Note that this setting is a firmware value within the battery itself, so will not be affected by any reinstallation of the operating system. It’s possible it could be hacked but to my knowledge there’s no published method of doing so, so it’s very unlikely to have happened.

Disk lifetime
Every modern hard disk/SSD records the number of hours it has been used, in hours, and this gives an indication of the number of hours the Mac has been powered-up (provided the disk hasn’t been replaced at some point, of course).

To discover this information, download the free-of-charge smartmontools app, right-click the installer, select Open, then opt to install the app.

Update 25 Jan 2017: Whoops, it looks like the smartmontools installation package is broken. Therefore, you’ll have to install Homebrew using the instructions on its home page, then within the same Terminal window you opened to do so (you’ll find the Terminal app in the Utilities folder of the Applications list of Finder), type brew install smartmontools. If you’ve already tried to install smartmontools via the installer package you’ll need to type the following instead: brew link −−overwrite smartmontools.

Following this, open a Terminal window (which you’ll find in the Utilities folder of the Applications list of Finder), and paste-in the following before hitting Enter:

smartctl -A /dev/disk0

The output might be confusing but look for the row that reads Power_On_Hours, and the the figure listed in the RAW_VALUE column at the very right. You might have to expand the Terminal window horizontally to make everything line-up.

This figure is approximately the number of hours the drive has been powered-up since it was installed in the computer. With my 1.5 year-old MacBook Pro I see a figure of 4607 hours, which translates to the equivalent of 192 days of solid usage – although this was obviously broken-up into periods when I was working. I use my Mac for around eight hours a day (work and play), so if you do the math (548 days * 8 hours per day) you’ll see this figure just about makes sense.

However, it’s not quite as simple as you might expect because modern battery-powered Macs feature Power Nap, which means the computer wakes-up silently even when computer is in sleep mode (such as when the lid of a MacBook is closed), in order to complete various tasks such as fetching email. Because of this, the hard disk might actually be awake even though the computer is not being used, thereby skewing the power-on figure from our perspective.

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Note that this setting is a firmware value within the disk itself, so will not be affected by any reinstallation of the operating system. It’s possible it could be hacked but to my knowledge there’s no published method of doing so, so it’s very unlikely to have happened.

Learning when macOS/OS X was installed
If the user you’re buying the Mac from has never reinstalled macOS/OS X then you can find out exactly when they first powered-up the Mac and completed the initial setup. Just open a Terminal window as described above and paste in the following:

ls -l /var/db/.AppleSetupDone

Then look at the date listed in the output, approximately in the middle of the line. On my MacBook Pro I see 28 Jun 2016, which doesn’t match with my 1.5 years of usage of this computer, but probably does mark the point at which I decided a complete reinstallation of OS X/macOS was required. Notably, this date doesn’t change when even major operating system updates are applied.

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Do you know of any other clever trick for working out how much a Mac has been used? Let me know in the comments below and I’ll add them in to this article at a later date.




Leave a comment...

That “complete reinstallation the MacOS” (I call clean install) its is a not-uncommon event, and is used by apple techs as a default method to address any problems by or variables. You point out that it resets some counts by the Mac related to these metrics you detail – Like hard disk, power-on hours, also reset too?

— Smith Jeffrey C. · Jan 23, 09:16 PM · #

Good point Smith Jeffrey. I’ve updated the article to point out that these are firmware values, so are not affected by software reinstalls. It’s possible they could be hacked but there’s no published method of doing so, so that’s unlikely to have happened.

Keir Thomas · Jan 24, 02:07 AM · #

The CoconutBattery app will give you much more information about the battery, including how much of the “design capacity” is still available. My daughter and I had our MacBook Pro batteries replaced within a couple of months of each other about 3 years ago, and I happened to look at both of them with CoconutBattery recently. My laptop spends about 95% of it’s time on a desk plugged in which actually is not ideal for battery life and capacity (I make a point to fully discharge it a couple of times a month). My daughter, a student, runs hers on the battery much more often. So, although my battery has fewer charge cycles, it is down to 71% of “design capacity” whereas my daughter’s, with more charge cycles, is still at over 90% of “design capacity” (they both have the same design capacity of 5770 mAh). (Caveat: I don’t know how accurate CoconutBattery is, and it may be that she simply got a “better” battery due to luck of the draw).
I read this article because I am in the market for a used MacMini. Since I will most likely replace whatever HD it has with an SSD and do a clean install, I don’t care about the HD usage. I don’t think that leaves me with anything quantitative in terms of wear and tear that I can check. Probably the best I can do, assuming it works OK, is a visual inspection for signs of it being dropped.

— Bruce Blakely · Jan 25, 07:11 AM · #

Hi Bruce

You’re missing the point re: replacing the disk. You can use the hours usage figure as a method of gauging how much the ENTIRE MAC has been used. Has it been used for maybe an hour a week? Or has it been used each day? This indicates how well-used the Mac is, and therefore how likely it is to continue working.

This isn’t just about finding out how much the disk and battery have been used!

Keir Thomas · Jan 25, 07:17 AM · #

The iStat app from has a battery module that will tell you how many cycles the battery has done, plus give an indication of the Health of the battery as a percentage.

It’s also pretty good at giving time left on current charge if you’re looking to replace what Apple just took away.

Michael Quinn · Jan 25, 11:53 AM · #

I have a 3 year old Macbook Air, OS installation date of 10/24/2014 but power cycle number is only 74. This is my work computer and while I do take it out occasionally, I almost always leave it at my desk plugged in. Definitely means take that power cycle number with a grain of salt and look at the other numbers as well.

— Eugene Kim · Jan 25, 03:24 PM · #

Nice article!
I’m just a bit curious about your statement about battery cycles:

Although it’s impossible to estimate, if I saw something like 300 cycles on a three year-old Mac then I would be very impressed.

I guess you will be very impressed by the 278 cycles my 5-year-old macbook pro reports right now…

Actually I also find that number hard to believe, I use this laptop 5 days a week for about 6 hours every day. It is mostly connected to an outlet, but every day it gets disconnected when I leave work.

— Floris · Jan 27, 12:57 AM · #

1000 cycles? LOL. Mine started to fail past 600 (2012 rMBP) and now instantly and unexpectedly dies around “25%” charge, requiring a restart. Not the first battery that’s failed this way.

5 years is far too long for a primary, working machine anyway. Only kept it so long as 1. was waiting for 2016 models to drop before buying, and, having now got one, 2. I’m too lazy to finish building it. Once I’m finally off it, I’ll eBay a hopefully-not-completely-dodgy battery† and (depending on whether or not that blows up) keep it as a spare or junk it. Or else just nuke it, flog it, and let some other mug eat the outrageously scammy price of an official Apple replacement.

One more thing: even unused batteries have a limited shelf life, so even a pristeen never-been-used 5yo machine isn’t going to have much distance left in it before it needs replacement/permanent mains anyway. It’s just chemistry.

† Caveat emptor: Chemistry also explodes! (Remember the Note!)

— has · Jan 30, 03:13 AM · #