Use the following formula
Pmt = L [ r ( 1 + r )n ] / [ (( 1 + r )n) - 1]
L = loan amount ($180,000)
r = monthly interest rate (APR/12)
n = the number of months financed (180)
I'm assuming that the APR is fixed for 180 months, the figures below do not take PMI, and taxes
Pmt = $1,617.89 for 179 months, and $1,618.06 for the last payment
Your total payments will be $291,220.37, and this includes $111,220.37 in finance charges.