## Calculating Payments

Interest Rate(r) = 13.5%

Periods Per Year(p) = 52 (compounding weekly)

Number of payments(n) = 157 (weeks)

Loan Amount(PV) = $12000

Periods Per Year(p) = 52 (compounding weekly)

Number of payments(n) = 157 (weeks)

Loan Amount(PV) = $12000

**The Excel Way:**`=PMT(r/p, n, PV) (reference)`

**The Mathematical Way:**`r(PV) / [1 - (1+r)^-n]`

**The Java Way:**## Calculating APR

Assuming the above, plus a Payment Amount(a) = $93.16

I have found there are a lot of ways of how to calculate APR floating around and none of them are very straight forward.

And even understanding the FDIC's rules on it can be a little hairy. My take is that you have to get it right to within .25% or .125% of however the FDIC calculates it, depending on the type of loan.

Here is an Excel Sheet with the Payment and APR formulas.

**The Excel Way:**`=RATE(n, a, PV) * p`

(reference)**A Mathematical Way:**` [(Interest payments + fees)/number of years] / Average amount borrowed`^{*}

(reference)^{*}In the reference site notice how they calculate the average borrowed.**The Java Way:**I have found there are a lot of ways of how to calculate APR floating around and none of them are very straight forward.

And even understanding the FDIC's rules on it can be a little hairy. My take is that you have to get it right to within .25% or .125% of however the FDIC calculates it, depending on the type of loan.

Here is an Excel Sheet with the Payment and APR formulas.

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