15 vs. 30-year mortgage calculator

Compare a shorter fixed repayment term with a longer one using the same borrowed amount. See the monthly payment for each term and the total interest if each loan is kept until payoff. The saved weekly selector fills both rates from a common survey date so you can compare historical scenarios without mixing dates.

Worked example from an official source

Source: Federal Reserve term comparison on a $200,000 loan.

Separate rate from repayment term

The comparison changes both the rate and the repayment period when you use the PMMS inputs. To isolate the term alone, type the same rate in both rate fields and calculate again. To compare two proposed loans, replace the survey averages with the note rates on your documents. The CFPB payment explanation identifies loan amount, term, and interest rate as the inputs that determine a fixed principal and interest payment. Survey observations provide context for those inputs but cannot establish pricing for your own application.

Read the monthly payment increase

The payment increase equals the shorter-term payment minus the longer-term payment. A positive number means the shorter loan requires a higher principal and interest payment each month under your inputs. That result excludes property taxes, homeowners insurance, mortgage insurance, and other charges. The shorter term also has fewer scheduled payments. Compare the monthly result with the full-term interest results rather than assuming that a lower monthly bill represents a lower total interest cost. The Federal Reserve term discussion explains this tradeoff between payment size and interest over time.

Use a common survey date

Choose one of the saved weekly observations to fill both rate fields. The selector changes the rates, then recalculates the comparison. Each value is from the Freddie Mac national series made available through FRED. The observations are weekly purchase mortgage averages. They are not cash-out, state, FHA, VA, or individualized refinance quotes. The tool shows the latest saved observation date separately from your selected scenario date. Editing the rates creates a user-entered scenario; it does not change the official data file or the published history.

Keep the full-term assumption in view

Total interest is the sum of all scheduled principal and interest payments minus the original principal. The interest savings result subtracts shorter-term interest from longer-term interest. It assumes no early payoff, extra payments, fees, or changes to the rate. If you compare a refinance, enter the unpaid balance and remember that this page starts a fresh term for each option. It does not model the existing loan that would otherwise continue. Use the homepage refinance tool to compare an existing remaining term with a proposed new loan. Closing costs can change the decision even when one option has less interest, so the payment comparison is only part of the review.

How it works

P is the borrowed principal, M is the monthly principal and interest payment, r is the monthly interest rate, and n is the number of monthly payments. At a zero interest rate, M = P / n. The CFPB payment explanation describes a fixed-rate payment that fully repays the loan by the end of its term. This is the standard amortization formula for that payment.

Total scheduled interest = monthly payment * number of payments - principal. Interest savings = 30-year interest - 15-year interest. Monthly payment increase = 15-year payment - 30-year payment. The Federal Reserve term comparison explains comparing interest and payments under different terms.