I had some spare time so I decided to create an Excel spreadsheet to keep track of my credit accounts (CC's, loans, etc) and it turned out quite nice.  The way I have it set up is that after inputting the CC information (e.g., opening date, balance, CL), the "Age" and "Util" values will automatically be generated.  Also, the formulas toward the bottom of the sheet calculate overall util four different ways (util across all accounts open and closed, util on all open accounts, util on all open and closed revolving accounts, and util on only open revolving accounts).  Also, oldest account age and AAoA are calculated and displayed in months and years.

Rather than emailing the spreadsheet, I have copied the formulas in a Microsoft Excel 2007 format and pasted them below.  You should be able to copy and paste the below information directly into Excel 2007 (I don't know if it will work on earlier versions).  When you first paste it into Excel, it will look pretty funky, but if you click the clipboard icon that appears at the bottom right corner of the area you pasted and click "Match Destination Format", it should look much cleaner then.  For the final touches, you'll want to change the format of the "Date Opened" column to a month/year format and then change the "Util" column to a percentage format (right click the top of the column and select "Format Cells").

Account Name	Date Opened	Age	Balance	Limit	Util	Type	Status
American Express Blue Cash Everyday	40645	=IF(B2<>"",(TODAY()-B2)/31, "")	284	3900	=IF(E2<>"", D2/E2, "")	Revolving	Open
Chase Amazon Rewards Visa #1	38443	=IF(B3<>"",(TODAY()-B3)/31, "")	0	12500	=IF(E3<>"", D3/E3, "")	Revolving	Closed
Chase Amazon Rewards Visa #2	39173	=IF(B4<>"",(TODAY()-B4)/31, "")	0	5500	=IF(E4<>"", D4/E4, "")	Revolving	Open
Citi Bank Dell Financial Services	39753	=IF(B5<>"",(TODAY()-B5)/31, "")	0	4000	=IF(E5<>"", D5/E5, "")	Revolving	Closed
Sam's Club GEMB Discover	39814	=IF(B6<>"",(TODAY()-B6)/31, "")	0	5850	=IF(E6<>"", D6/E6, "")	Revolving	Open
Schools First FCU #1	38657	=IF(B7<>"",(TODAY()-B7)/31, "")	0	2900	=IF(E7<>"", D7/E7, "")	Revolving	Open
Schools First FCU #2	38657	=IF(B8<>"",(TODAY()-B8)/31, "")	0	2900	=IF(E8<>"", D8/E8, "")	Revolving	Open
Schools First FCU #3	38657	=IF(B9<>"",(TODAY()-B9)/31, "")	0	3900	=IF(E9<>"", D9/E9, "")	Revolving	Open
Sear's Citi Bank Discover	40026	=IF(B10<>"",(TODAY()-B10)/31, "")	0	6000	=IF(E10<>"", D10/E10, "")	Revolving	Closed
Student Loan #1	40391	=IF(B11<>"",(TODAY()-B11)/31, "")	8500	8500	=IF(E11<>"", D11/E11, "")	Installment	Open
		=IF(B12<>"",(TODAY()-B12)/31, "")			=IF(E12<>"", D12/E12, "")
		=IF(B13<>"",(TODAY()-B13)/31, "")			=IF(E13<>"", D13/E13, "")
		=IF(B14<>"",(TODAY()-B14)/31, "")			=IF(E14<>"", D14/E14, "")
		=IF(B15<>"",(TODAY()-B15)/31, "")			=IF(E15<>"", D15/E15, "")
		=IF(B16<>"",(TODAY()-B16)/31, "")			=IF(E16<>"", D16/E16, "")
		=IF(B17<>"",(TODAY()-B17)/31, "")			=IF(E17<>"", D17/E17, "")
		=IF(B18<>"",(TODAY()-B18)/31, "")			=IF(E18<>"", D18/E18, "")
		=IF(B19<>"",(TODAY()-B19)/31, "")			=IF(E19<>"", D19/E19, "")
		=IF(B21<>"",(TODAY()-B21)/31, "")			=IF(E21<>"", D21/E21, "")
		=SUM(C2:C21)	=SUM(D221)	=SUM(E2:E21)	=AVERAGE(F2:F21)	(all accounts)
					=AVERAGEIF(H2:H21,"Open",(F2:F21))	(all open accounts)
					=AVERAGEIF(G2:G21, "Revolving", F2:F21)	(all revolving)
					=AVERAGEIFS(F2:F21, H2:H21, "Open", G2:G21, "Revolving")	(open revolving)
		=MAX(C2:C21)	Oldest (in months)
		=C22/COUNT(C2:C21)	AAoA (in months)
		=C27/12	Oldest (in years)
		=C28/12	AAoA (in years)

NOTE: For the overall util formulas to calculate correctly, the value under the "Type" column should be either "Revolving" or "Installment" and the value under the "Status" column should read either "Open" or "Closed".

I thought this would be helpful to others so I'm just passing it along.  Let me know if you have any problems getting it to work.

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