Where do I find the *actual* blockchain size?
The blockchain sizes of Bitcoin, Litecoin, Dash, Dogecoin, Peercoin and Namecoin are listed here at https://bitinfocharts.com/
(scroll down to Blockchain Size)

As of today (2015-07-12) the sizes are (sorted by market capitalization):

Bitcoin             Litecoin          Dash              Dogecoin          Peercoin          Namecoin
44.73 GB            4.64 GB           1.01 GB           11.41 GB          0.4191 GB         2.64 GB
$4,477,078,707 USD  $209,054,841 USD  $23,217,866 USD   $20,686,200 USD   $15,897,328 USD   $9,888,883 USD


Note that Dogecoin, although very new, has a very big chain already, where Peercoin has by far the smallest.

Your question

On my hard disk the .bitcoin directory uses 45 GiB = 48 GB.