How is a loan payment calculated?
Loan payments are calculated using the standard amortization formula: M = P[r(1+r)^n]/[(1+r)^n-1], where P is the principal loan amount, r is the monthly interest rate (annual rate divided by 12), and n is the total number of monthly payments. Each payment consists of two parts: interest on the remaining balance and principal repayment. In the early months, a larger portion of each payment goes toward interest, while later payments apply more toward the principal. This is why making extra payments early in the loan term has such a significant impact on total interest paid. For a zero-percent interest loan, the calculation simplifies to dividing the principal by the number of months. Understanding this formula helps borrowers see exactly how their money is allocated over the life of the loan and why longer terms cost significantly more in total interest despite having lower monthly payments.