Field showing current file size?

If being able to pull out this information into a field via a formula would be helpful though I would suggest adding it as feedback on our User Voice page. User Voice is a tool our product team uses to track user interest in new features and enhancements to existing features, they have done some recent work with formulas based on user feedback to extend the options available that found their start in User Voice and the community threads here. The Quick Base User voice can most easily be accessed from the My Apps page in Quick Base by clicking on the orange Feedback tab that appears on the right of the page or at http://quickbase.uservoice.com by signing in with your Quick Base credentials.

If you do put in a request for that to be added to formulas I would suggest dropping a link to your suggestion in this thread so that other community members can add their vote and show their support.