Problem with file size

[oliverm81709700]

I have searched to know avail here for answers as to why photoshop is not showing me my image size in MB.  I am currently having to resize images for 500px and my website and it won't show me how any MB my file is.  Maybe I don't know how to read it but when I used photoshop on my laptop I was able to select image size and at the top left corner it would show me my file size in megabytes but now that I have a desktop it shows me in (M).  I don't even have a clue as to what (M) is short for, because if I export an image to my desktop it shows me in MB and it is completely different from what is written on photoshop.  Here is an example.  I exported an image and used the get info from the right click on my Mac and the image size stated it was 35.8 MB and then I opened it in photoshop and it stated it was 227.0M.  Now this is a problem because I don't know how to convert that to MB and size my image so it can be uploaded online. 

Sorry for the rambling, but any help would be greatly appreciated.

[D Fosse · Accepted solution]

That sounds like normal jpeg data compression. When you open a jpeg it is decompressed and essentially stops being a jpeg - when open it's just a pixel array like any other.

It only becomes a jpeg the moment you save it to disk, and then the jpeg format uses very aggressive data compression to reduce storage file size.

If you need a certain target file size for web, what you're looking for is the compressed size on disk.

[rejittiachan]

You can use File > Export > Save for Web (Legacy) option. (Shortcut Shift+Alt+Cmd+S). Down left, you can see the size of the to be exported file.

Hope this helps.

[oliverm81709700]

Thank you for for the answer.  I understand now.

[josephlavine]

I ran a quick test using Export > Save for Web (Legacy) and using the settings for the attached image shows that I should have a JPEG that is roughly 1.8M (1.8MB), and when I check the closed file size on my desktop it matches.  However, as D Fosse mentioned, when the file is opened it is uncompressed and will be larger.

[oliverm81709700]

Awesome!  Thanks for the explanation.