How do I make a formula to find a loan amount that I can get if I know the :
Interest rate
the payment amount I can make
30 year loan monthly payments
For example, assuming a US loan or similar (specifically not
Canadian), if the nominal interest rate is 6% and the desired monthly
payment is $1200
=rounddown(pv(6%/12, 30*12, -1200), 0)
ROUNDDOWN() above rounds down to a dollar amount. I round down in
order to ensure that the monthly payment does not exceed $1200.
Note that I specify the "nominal interest rate", not the APR.
Sometimes, the advertised APR includes amounts that are not used in
computing the periodic loan payment (or in your case, the loan amount).