Essentials Student Loan Payoff Spreadsheet Template for Google Sheets & Excel

The loan - balance, rate, scheduled payment and the date payments start - plus the field this build exists for: an extra monthly amount towards the principal. Underneath, the first month's interest, the total paid with that extra applied and the total interest, both summed from the schedule rather than estimated. Summing rather than estimating matters here because an extra payment changes the shape of the loan rather than scaling it: every month it shortens, the remaining months carry less interest, and a formula that multiplied a payment by a term would miss that entirely.

A row per month across the term, and the important thing about it is that it carries both futures in the same table. For each month: the payment, the principal and interest split, the extra applied, the balance with the extra - and beside it, the balance without it and the interest that path would have charged. Reading the two balance columns against each other is the whole argument. They separate slowly at first and then faster, because every extra amount of principal removes all the interest that amount would have generated for the rest of the loan. The month where the with-extra column reaches zero while the other is still substantial is the clearest statement of what the extra payment bought. The schedule stops where the loan does rather than running to the end of the sheet.

Six figures. The balance, the monthly payment with the extra included and the total interest with the extra applied on the top row; the date the loan finishes, how many months sooner that is than the standard schedule, and the interest that avoids on the second. The second row is the reason to add an extra payment at all, and it is where the arithmetic stops being abstract - a number of months and a sum of interest rather than a slightly lower balance each period. The payment figure combines the scheduled amount and the extra deliberately: what leaves your account is one number, and separating them on a dashboard would misrepresent the commitment you are actually making.