The simple calculation here is: 

       (Current Assets - Cash*)
  ---------------------------------                 
  (Current Liabilities - ST Debt**)

  * Cash = cash & equivalents, marketable securities, and short-term investments
  ** Short-term Debt = notes payable and current portion of long-term debt

Ready for an example? 

  Intel Fiscal Year 1999

  Cash & Cash Equivalents= $11.8 bil
  Current Assets =  17.8
  Short-term Debt=   0.2
  Current Liabilities=   7.1

                   (Current Assets - Cash & Equiv.) 
  Flow Ratio  = ---------------------------------------
                (Current Liabilities - Short-term Debt) 

  = (17.8 - 11.8) / (7.1 - 0.2) 

  = 0.87

  The Flow Ratio is just one of many measures of quality, but we think it makes an
  excellent starting point. Again, we want companies that have a Flow Ratio less than
  1.25, and ideally less than 1.0. 

  The Flowie is your friend. By running it, you'll be measuring how tightly the company
  manages cash as it flows through their business. Are they being lazy in collecting
  their bills? Are they being sloppy in managing their inventory? Are they in such a
  weak financial position that their partners demand cash payments from them
  upfront? If so, look out... this probably isn't a darling horse nor a long-term winner.