# What is the equation that Excel uses for the IPMT(...) function?

I am looking for the equation that Excel uses to calculate the IPMT(...) function.
I have been searching via bing and google and haven't found this answer.
Would appreciate some help.
Thank you

## Question Info

Last updated March 15, 2020 Views 6,965 Applies to:

If you would like to include the equation for the monthly payment on a simple loan

(fv=0, type =0)

'Tn is the length of the loan.

'n is the period in question.

'pv = present value

'rt = Interest Rate

=(pv*rt*((rt + 1)^(Tn + 1) - (rt + 1)^n)) / ((rt + 1)* ((rt + 1)^Tn - 1))

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If you want just the basic equation, (fv=0, type=0),  then...

IPMT = pmt + (1+ir)^(n-1) *(pv * ir - pmt)

You could add the equation for Pmt into the above if you wish.

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