You need to look at either your ACD logs or should you have a call logger ie Tiger 2000 you can look at historical data in 15 minute blocks over a 24hour period. I have recently predicted our demand graphs by running Tiger 2000 over a 6 month period producing one file for each day of the week. The logger allows you to save the files as text files which can then be manipulated using Excel. Open the the text file with Excel which will start the import wizard. Tell the wizard that your file is comma delimited and the spreadsheet does the rest. Divide the calls in each 15 Minute Block by 26 ( the number of weeks in 6 months) and this will give you an average call rate for each day in 15 minute blocks. then use staffing data to predict your staff level in 15 minute blocks. Hope this helps.