The monthly cost of a $20,000 car loan will depend on your repayment period and the APR.
If you choose a repayment period of 48 months with a 5.06% APR (based on a good credit score), your monthly payments would be about $452 before sales tax.
However, increasing the loan term or having a different APR can greatly affect monthly payment amounts. For example, a 72-month loan term would reduce your monthly payment to $316.
There are loan payment calculators online that you can use, or you can use this formula:
Payment amount = P (r (1+r)^n) / ( (1+r)^n -1 )
P = Initial principal or loan amount (in this example, $10,000)
r = Interest rate per period (in our example, that’s 7.5% divided by 12 months)
n = Total number of payments, or the term length of your loan