What Affects Amortization Schedule

The single biggest factor affecting amortization schedule is interest rate, which increases the total amount paid over the loan term, as seen in a $200,000 mortgage with a 4% interest rate, resulting in a monthly payment of $955 for 30 years, totaling $343,739, whereas a 3.5% interest rate would reduce the total to $333,144.

Main Factors

• Interest rate — the higher the interest rate, the higher the monthly payments and total amount paid, increasing the total cost, as a 1% increase in interest rate on a $200,000 mortgage can increase the total cost by $30,000 over the loan term, as evidenced by the difference between a 4% and 3.5% interest rate in the previous example.
• Loan term — the longer the loan term, the smaller the monthly payments, but the larger the total amount paid, as a 30-year mortgage on a $200,000 loan at 4% interest would have a monthly payment of $955, whereas a 15-year mortgage would have a monthly payment of $1,479, with the 30-year mortgage resulting in a total of $143,739 in interest, compared to $57,357 for the 15-year mortgage, as calculated by Fannie Mae.
• Loan amount — the larger the loan amount, the larger the monthly payments and total amount paid, as a $300,000 mortgage at 4% interest for 30 years would have a monthly payment of $1,432, compared to $955 for a $200,000 mortgage, with the larger loan resulting in a total of $215,608 in interest, compared to $143,739 for the smaller loan, as reported by Freddie Mac.
• Payment frequency — the more frequent the payments, the smaller the total amount paid, as making bi-weekly payments on a $200,000 mortgage at 4% interest for 30 years would save $29,000 in interest over the life of the loan, compared to making monthly payments, according to Bank of America.
• Compounding frequency — the more frequent the compounding, the larger the total amount paid, as daily compounding on a $200,000 mortgage at 4% interest for 30 years would result in a total of $346,644, compared to $343,739 with monthly compounding, as calculated by Wells Fargo.
• Prepayment penalties — the presence of prepayment penalties can decrease the benefit of making extra payments, as a $200,000 mortgage with a 4% interest rate and a 2% prepayment penalty would result in a penalty of $4,000 for paying off the loan early, reducing the savings from making extra payments, as noted by the Federal Reserve.
• Credit score — a higher credit score can result in a lower interest rate, decreasing the total amount paid, as a borrower with a 750 credit score may qualify for a 3.5% interest rate on a $200,000 mortgage, compared to a borrower with a 650 credit score who may qualify for a 4.25% interest rate, resulting in a difference of $24,000 in total interest over the life of the loan, according to Experian.

How They Interact

The interaction between interest rate and loan term can amplify the total amount paid, as a 30-year mortgage at a 4% interest rate would result in a total of $143,739 in interest, whereas a 15-year mortgage at the same interest rate would result in a total of $57,357 in interest, demonstrating the impact of loan term on total interest paid. Additionally, the interaction between payment frequency and compounding frequency can cancel each other out, as making bi-weekly payments on a mortgage with daily compounding may result in similar total interest paid as making monthly payments on a mortgage with monthly compounding. Furthermore, the interaction between credit score and interest rate can reduce the total amount paid, as a borrower with a high credit score may qualify for a lower interest rate, resulting in lower monthly payments and total interest paid.

Controllable vs Uncontrollable

The controllable factors are loan term, payment frequency, prepayment penalties, and credit score, which can be controlled by the borrower through their choices and financial decisions. For example, a borrower can choose a shorter loan term, make bi-weekly payments, avoid loans with prepayment penalties, and work to improve their credit score to reduce their interest rate. The uncontrollable factors are interest rate, loan amount, and compounding frequency, which are determined by the lender and market conditions. However, borrowers can still take steps to mitigate the impact of these factors, such as shopping around for the best interest rate, considering a smaller loan amount, and understanding the compounding frequency used by their lender.