How to show rsync progress

Answer: Use the --progress option

rsync --progress [source] [destination]

For each file being copied you'll get the following info, updated along the way:

[file size] [current progress %] [transfer speed] [time remaining]

Here's an example output:

test_file1
    14708627 100%  233.73MB/s    0:00:01 (xfer#1, to-check=1/2)
test_file2
   459243520  42%   72.68MB/s    0:00:08

As a shortcut, you can use -P instead of --progress, but with a little caveat.

Have in mind that -P  is equivalent to --progress --partial. In most cases, this is just fine, since including --partial tells rsync to keep incomplete files at the destination in case the transfer is interrupted. To quote man pages:

--partial

By default, rsync will delete any partially transferred file if the
transfer is interrupted. In some circumstances it is more desirable to 
keep partially transferred files. Using the --partial option tells 
rsync to keep the partial file which should make a subsequent transfer 
of the rest of the file much faster.

Human-readable numbers with -h

The first column in the progress output shows the file size, and by default, it is in bytes. In order to display file sizes in a more human-readable format, you can use -h  or --human-readable.

rsync --progress -h [source] [destination]

Using -h gives us the following output (note the file size in megabytes):

test_file1
      14.71M 100%  237.69MB/s    0:00:00 (xfer#1, to-check=1/2)
test_file2
     904.92M  84%  215.90MB/s    0:00:00

File transfer stats with --stats

If we call rsync with the --stats option, at the end of the transfer we get helpful stats about the overall transfer process. Here's an example:

rsync --stats --progress -h [source] [destination]

test_file1
      14.71M 100%   82.82MB/s    0:00:00 (xfer#1, to-check=1/2)
test_file2
       1.07G 100%   74.62MB/s    0:00:13 (xfer#2, to-check=0/2)

Number of files: 2
Number of files transferred: 2
Total file size: 1.09G bytes
Total transferred file size: 1.09G bytes
Literal data: 1.09G bytes
Matched data: 0 bytes
File list size: 41
File list generation time: 0.001 seconds
File list transfer time: 0.000 seconds
Total bytes sent: 1.09G
Total bytes received: 64

sent 1.09G bytes  received 64 bytes  75.07M bytes/sec
total size is 1.09G  speedup is 1.00