certutil -hashfile [path\]filename MD5
The tool is built into Windows 7 and above, and Server 2008 and above (at least). Tools like it are included in other OS's, but I'm sharing the above for Windows users.
Regardless of what OS you use, for more on why knowing the checksum can be useful (and why comparing file sizes instead may not be enough), and especially with regard to some interesting info about installers for CF2016 and CF11, do read on.
Why knowing the checksum is valuable
There are at least a couple of uses of knowing/finding the MD5 checksum for a file. (It's basically a hashing of the file contents into a small string that can be used to determine whether a given file shares the checksum with another file.)
You may have noticed that web sites often will offer the checksum value of a file you're about to download, with the intent that you could check that after downloading it--to make sure you got the file they intended you to get. It's been my observation that most folks never bother, but at least now if you want to (but didn't know how, on Windows), you can. (Such tools exist for other OS's, of course. I leave that as an exercise for the interested reader.)
Another reason knowing how to easily get the checksum can be when you are wondering if an installer you have is the same one that someone else says they have or used (see below for a real example of such confusion). The file the other person has may have the same name (and could even have the same date and file size) and yet NOT be identical. Getting the checksum is the way to know. (Of course, if you had both files you could do a compare, but this is typically still faster.)
Why this can be helpful, especially with CF installers
But this can be especially helpful with ColdFusion installers, for a number of reasons. I was helping two different folks today with questions about their CF11 and CF2016 installers (because in both cases, there were different installers over time, even for the same version and OS and bit-level), and it's what prompted me to share that info above with them, and now to create this post.
For instance, did you know that with CF2016, there have been 3 installers?
The original installer (in early 2016) included the API Manager (which made it a huge 1g plus!, and it did not happen to work yet for Windows 10/Server 2016). Then in Dec 2016, a new installer came out (for all OS's) where they thankfully removed the API Manager, bringing it down to several hundred meg (still to large for some tastes, but that's not the point of this post).
Then finally in Apr 2017 yet another installer (for Windows only) was released which DID add support for Windows 10 and Server 2016.
So when you are installing CF, it would help to know which installer is which. The names are all the same (for a given version on a given OS and bit level.)
Of course, Adobe would typically just put the latest one on their site, but people often had downloaded it in the past and were then using it later, and didn't realize it was not "the same". Or I help people often who install ColdFusion on a new machine using an installer they had used on a previous machine, some years ago.
And note that there were different CF11 installers over time, also. One had mistakenly turned on session persistence, for instance, which was corrected by a new installer in Jan 2015.
And that blog post about the mistaken CF11 installer update indicates that it was released in Dec 2014, as a replacement of the original CF11 installer from early 2014. It had added update 3, among other things, and in fact these new installers will also come with the latest available ColdFusion and JVM update. That's another reason to know which installer you are using. (Sad that it's been potentially confusing, yes.)
Finally, no, Adobe no longer offers the installers for CF2016 or before on their site, now that CF2018 has come out. For those, see the CFMLRepo site, which offers installers back to CF 1.5! BTW, while as of the original writing of this post, it did not have that latest CF2016 installer from Apr 2017 (for Windows 64-bit supporting Windows 10 and Server 2016), I since got it uploaded there.
Getting the checksum
So again, here's how to get the sum for that latest CF16 64-bit windows installer I had:
If you're doing the check in the same directory as the file, then you can leave off the path, obviously.
Also, in some versions of Windows, that final arg (for the kind of hash algorithm) is case-sensitive, so use a capitalized value for maximum reliability. Finally, note that if you want instead to get a SHA-1 hash, you could replace the MD5 with SHA1. Use "certutil -hashfile /?" to see more help and other hash algorithms supported.
In my case, that command above reported:
CertUtil: -hashfile command completed successfully.
Again this is the version of the CF2016 installer for Windows 64-bit which WAS able to install on Windows 10 and Server 2016.
(If somehow this tool doesn't work for you, there are many available free tools you can find to calculate checksums and CRCs, for all operating systems.)
Hope all that's helpful.