This article originally appeared in TidBITS on 2011-07-05 at 2:55 p.m.
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How Long Will Lion Take to Download?

by Michael E. Cohen

In the fabled Good Old Days, figuring out how long it would take to get your hands on the discs containing the latest Mac OS X upgrade involved either determining how long it would take you to drive to the nearest retail outlet selling the package, or monitoring a delivery tracking page in your Web browser to see where the shipment you ordered containing the discs currently was on its journey to your eagerly awaiting Mac.

In these Good New Days, however, the latest upgrade to Mac OS X 10.7 Lion will be available only from the Mac App Store, which means you can get your hands on it instantly — where “instantly” means as fast as your Internet connection to Apple’s servers can download it.

For most of us, “instantly” will still mean a considerable wait, so you probably don’t want to purchase Lion if you have to walk out the door with your laptop a few minutes later. But how long will you have to wait as the rough beast slouches its way onto your hard disk? It’s not hard to come up with a reasonable estimate.

First, you need to find out how much throughput you get from your Internet connection — not how much throughput your service provider says you get, but how much you actually get, which may vary with time of day. (Early evening is often the worst time for residential Internet connections, as everyone heads to Netflix to stream videos.) Fortunately, there are a number of Web sites that can test your connection, such as [1]. You can run a quick test on that site (it only takes thirty seconds or so) to find out the throughput of your connection in Mbps (megabits per second).

Once you know that, you need to know how big the download is. Fortunately, that is not a big secret: the Mac OS X 10.7 Lion installer is known to be 3.76 GB. With that information, you can whip out a number 2 pencil and a pad of paper and do some quick ciphering — or you can go to another site that will do it for you, such as Derek Tsang’s Download Time Calculator [2]. Simply plug in the size of the download, and the throughput of your connection, and hit the Get Download Time button. You’ll get a reasonable approximation of how long it will take for the Lion installer to make it onto your Mac. (For a sense of how long the download would take on various standard Internet connections, check out the Gaijin Download Time Calculator [3].)

Of course, the estimate you get is only provisional: The download speed also depends on the throughput of the Mac App Store servers and Internet connections, along with the route between you and the Mac App Store. As we all know, those variables can vary. But at least you’ll know the least amount of time it might take, and be able to plan your day accordingly.