Reducing converted Mobi filesizes?

[VirgoGirl]

Hello!

If this question should be elsewhere, I'll ask there.

I'm considering a Kindle Paperwhite to "replace" (but not throw away) my Kobo Touch. As the Kindles are all internal memory only, I've been playing around with Calibre and mobi conversions to see file sizes.

With my Amazon direct purchases, the original file sizes are smaller than when I run them through Calibre to rename and convert to the Paperwhite settings. When I run the same files thru to convert to epub - which makes the file sizes 1/2 that of the original mobis - then back from epub to mobi, I still wind up with the same file size as I would if I were to do a direct convert from .azw mobis to calibre mobis.

Is there some way to tweak the converted files to either have them match the original Amazon file size, or even make them smaller than that? Space is an issue, and I am a hoarder.

[Katsunami]

You don't have to convert AZW or AZW3 to mobi.

AZW and AZW3 are the KPW's native format and you can send them from Calibre as-is.

Right-click on the device icon, and select "Configure this device".

Check AZW3, AZW, and Mobi, and put them in that order, from the top. Uncheck the rest. Calibre will send any of those files. Other files will be sent by converting to AZW3 first.

[GoSharks]

@VirgoGirl-
You might check to be sure that when you do your mobi conversion in Calibre that you have selected the output to be 'new' instead of 'both'....the 'both' setting will give you a book file that includes both 'old' mobi and 'new' AZW3, hence twice the size.

[VirgoGirl]

I convert the awz files because I add things like series names and book summary in metadata. I don't use Calibre to send books to the readers, I only use it to convert.

@Gosharks, I had no idea I could do that. Thank you!! Um, do you know how I set that up? I'm poking around Calibre but can't find it.

Ah, no found it- finally.

Nope, that doesn't work - I have an original file size of 297kb, a converted files size of 323kb. >

[Katsunami]

I still don't understand.

If you only want to add metadata, then just add the data, and use Polish Books. Tick the "Update metadata" checkbox, and your book will be updated. (Polish Book supports EPUB and AZW3.) Then you can get the book to your reader whatever way you want, including metadata, without converting.

The reason why your file size in MOBI format is bigger could be because of stylesheets. If I remember correctly, MOBI does not support linked stylesheets like AZW3 and EPUB do. So, if your book has 30 files inside that each link to the same stylesheet for their markup, that link will be replaced with the actual contents of the stylesheet on conversion, making the files bigger.

[VirgoGirl]

WOW! I had no idea I could do that! I currently have a Kobo, so I have been converting the epubs all this time just to add metadata and series names.

Looking for "Polish Books"..

Found it, but, it says it's only useable on azw3 or epub files. When I bring in the awz file, it;s converted to mobi.

[Katsunami]

Originally Posted by VirgoGirl

WOW! I had no idea I could do that! I currently have a Kobo, so I have been converting the epubs all this time just to add metadata and series names.

Looking for "Polish Books"..

Found it, but, it says it's only useable on azw3 or epub files. When I bring in the awz file, it;s converted to mobi.

You probably have this option ticked:

"Preferences -> Change Calibre Behaviour -> Adding books -> Automatically convert books to output format"

If you tell Calibre that you have a KPW in the intro wizard, without doing anything else, it will assign MOBI as the top format. If you have the above option checked, any non-MOBI book will be converted on import.

Find that option and untick it.

Connect your Kindle, and right-click "Device". Select "Configure this device"

Uncheck every format, except AZW3, AZW, and MOBI, and put them in this order.

Now Calibre will not immediately convert any incoming books, and it will send (or convert to before sending) AZW3 by default. If the book is AZW3, AZW or MOBI file already, it'll send it immediately. If it's not, then Calibre will try to convert it to AZW3, AZW or MOBI (in that order) before sending.

By the way: many "AZW" books are actually AZW3, especially the newer ones, but they can have an AZW3 extension.

You can, actually, convert a non-AZW3 file to AZW3, and then use Polish Books.

(I still tend to read that option's name with the wrong pronounciation... it has nothing to do with books from Poland...)

[GoSharks]

@VirgoGirl-
As an aside (I have no answer for your file size issue, sorry), if you are converting your books to a format for a Paperwhite it is recommended to convert to AZW3 directly and not to mobi (old, new, or both)...especially if converting from EPUB. (apparantly AZW3 is 'closer' to EPUB so Calibre doesn't take as long and requires less work, per Kovid)

[Katsunami]

Also, MOBI does not support a lot of stuff with regard to layout that AZW3 does.

If you convert from AZW3 or EPUB to MOBI, you'll certainly lose a lot of markup. However, EPUB does support some stuff that can convert *really* badly to AZW3 (or maybe it converts fine, but the Kindle botches it up when displaying) for some reason, and then losing the markup by converting to MOBI is actually preferable.