checking local file size

I know this isn't a php question (though I'm using PHP for the server side... does that count?). I'm hoping though that some of you guys are just as experienced in ajax as you are PHP, because I can't find any good ajax forums. you can respond to me personally if needed, to keep it off the php list.... my question: I know there are alot of ajax/php upload progress bars out there, but they're either complicated, unreliable, or just generally don't fit my needs. Thus, i'm making my own. One problem I'm running into though, is how to check the local file size as compared to the uploaded file size. I can check and display the total uploaded size (ie, 437kb uploaded so far...), but to get the percent, I have to know the total size - BEFORE it's fully uploaded. I would like to say "437kb of 932kb uploaded so far"... but how do I get the "932" from the local file? It doesn't do too much good to say how much has been uploaded if they don't know how much is left... I know it's possible (most other meters do this) - I just can't figure out how. any hints? Thanks