Total Cost of Student Loan Calculator
The Sticker Price Is Never the Real Price
A $30,000 student loan never actually costs $30,000 to repay — interest adds to that figure every month for the life of the loan, and depending on the term, the total can run anywhere from roughly a third more than the original balance to well over double it. This calculator multiplies the fixed monthly payment by the number of payments to show the full lifetime cost in one figure, alongside interest expressed as a percentage of the original principal.
The Formula
The monthly payment itself comes from the standard amortization formula, M = P × [r(1+r)^n] / [(1+r)^n − 1], and total interest is simply total cost minus the original principal.
Total Cost Grows Faster Than Term Length
| Term | Monthly payment | Total cost | Total interest | Interest as % of principal |
|---|---|---|---|---|
| 10 years | $333.06 | $39,967.38 | $9,967.38 | 33.2% |
| 15 years | $253.16 | $45,568.27 | $15,568.27 | 51.9% |
| 20 years | $214.93 | $51,583.04 | $21,583.04 | 71.9% |
Stretching this loan from a 10-year to a 20-year term more than doubles the interest paid as a share of principal, even though the rate never changes — a longer term trades a lower payment for meaningfully more total cost.
Where This Calculation Matters
- Comparing loan offers on lifetime cost — a lower advertised rate with a longer term can still cost more in total than a higher rate on a shorter term.
- Deciding whether to extend or shorten a term — seeing total cost side by side with monthly payment makes the tradeoff concrete rather than abstract.
- Evaluating whether extra payments are worth it — this figure sets the baseline that a payoff acceleration strategy is trying to beat.
How to Use This Calculator
- Enter the loan amount in dollars.
- Enter the annual interest rate as a percentage.
- Enter the loan term in years.
- Select Calculate to see total cost, total interest, and interest as a percentage of the original principal.
Related Calculations
See the monthly figure on its own with the Student Loan Payment Calculator, or test how extra payments shorten this total with the Student Loan Payoff Calculator.