I recently calculated how long it would take to pay off a loan, and I would like to have someone check my math to make sure I'm doing it right.
I used the formula below: (i = APR/12, b = total balance due today, p = monthly payment amount)
n = ln((1 - i) * (b / p)) / ln(1 + i)
to calculate how many payments it would take to pay off the loan. Is this formula correct?
Also, there are multiple loans with different interest rates that I want to calculate how long the payoff would take overall. Would summing the balances together and taking the mean of the interest rates provide an accurate calculation with the above formula?
This isn't homework, I'm doing this calculation for real-world purposes.