# How to add interest monthly in Excel?



## Cassfax (Dec 15, 2009)

I need a formula that will add 2% interest every 30 days to outstanding invoices. I have no idea where to begin. 
Please Help!


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## macropod (Apr 11, 2008)

Hi Cassfax,

Is that 2% per month simple interest or compunding interest?

Where the Invoice Date is in A1 and the Invoice Amount is in B1:
For simple interest calculated monthly-
=B1*(1+DATEDIF(A1,TODAY(),"m")*0.02)
For compound interest, where the annual rate of interest compunds to 24%-
=FV(1.24^(1/12)-1,DATEDIF(A1,TODAY(),"m"),0,-B1)
For compound interest, where the monthly rate of interest is 2%-
=FV(0.02,DATEDIF(A1,TODAY(),"m"),0,-B1)


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## Cassfax (Dec 15, 2009)

Thanks for your help. It worked like a charm!
One more question, I want the whole row to change colour when the invoice is over 30 days. I've figured out how to make the cell change colour but not the whole row. Can you help with this?

Thanks


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## macropod (Apr 11, 2008)

Hi Cassfax,



> I've figured out how to make the cell change colour but not the whole row. Can you help with this?


You apply the same conditional format to every cell on the row.


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## Cassfax (Dec 15, 2009)

I actually figured it out right after I wrote to you. Thanks again for all of you help. Much appreciated!


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