title_body: How can I upload my 100+ ebook collection to kindle cloud? I would like to upload all the books I have stored in my calibre library to kindle's cloud so that I can synchronize my reading (whispersync "sync to last page read" function) across my android and kindle voyage. Is this possible? 
  
  I have seen the email to kindle function but have read that this can cost money and am unsure if I will have to do each book individually. I live in Australia and am confident with calibre use. None of my books have DRM.
  
  This link provided by Woeitg: http://the-digital-reader.com/2015/02/07/upload-ebooks-documents-kindle-account/ Cleared up my confusion about emailing to kindle costing money. It seems this only applies only to kindle devices using 3G. appending the '.free' to the email ensures only wifi is used and no charges are applied.
upvoted_answer: If you use the Send to Kindle function, your books may end up stored as Documents. Kindle ownership gives 5 GB Cloud storage, so log into your Cloud Storage first and see how much you are already using (all your Documents back up here). If you want more storage, you have to buy it.
  
  How to do it? I'd use Calibre's own download to disk function to put them on my computer, locate the files and right click to use the Send to Kindle. Yes, 100 books is a lot, but if you want to send big batches of data, I'd check with Amazon Customer service first to see if there is a way to do that. I suspect not unless you submit zip files, since they won't want their system flooded.