The short answer
A $30,000 student loan at 5.5% costs $325.58/month on the Standard 10-year plan, with $9,069.46 in total interest. Stretching to the 25-year Extended plan drops the payment to $184.23/month but nearly triples total interest to $25,267.87. Going the other direction, adding just $100/month in extra payments to the 10-year plan saves $2,753.32 in interest and pays the loan off 2.8 years early.
Key takeaways
- The Standard 10-year plan minimizes total interest among the fixed-term options; every year added to the term lowers the payment but adds meaningfully to lifetime interest.
- Extended (25-year) repayment on $30,000 at 5.5% costs $16,198.41 more in total interest than Standard — a real trade-off for a payment that's $141.35/month lower.
- Extra payments are one of the highest-leverage moves available: $100/month extra on the Standard plan here saves more in interest ($2,753.32) than a full year of the extra payments themselves would cost ($1,200).
- Income-driven and graduated plans trade a lower or reshaped near-term payment for higher total interest (or forgiveness after 20–25 years) — compare the actual numbers rather than assuming a lower payment is automatically the better deal.
Comparing repayment plans
On a $30,000 loan at 5.5%, here is how the standard plan options compare:
| Plan | Monthly Payment | Total Interest |
|---|---|---|
| Aggressive (5 years) | $573.03 | $4,382.09 |
| Standard (10 years) | $325.58 | $9,069.46 |
| Extended (25 years) | $184.23 | $25,267.87 |
The pattern is the same one that shows up in every amortizing loan: a lower monthly payment always means more time for interest to accrue, so total interest rises. The Aggressive 5-year plan pays the least interest overall but demands nearly double the Standard plan's monthly payment. Extended repayment can make sense if the lower payment is genuinely necessary for your budget, but it should be a deliberate trade-off, not a default — going from 10 to 25 years here costs an extra $16,198.41 in interest for a $141.35/month reduction.
The outsized impact of extra payments
Standard 10yr: $325.58/mo → $9,069.46 total interest, 120 months
+$100/mo extra: $6,316.14 total interest, 86 months
Savings: $2,753.32 interest, 34 months (2.8 years) faster payoff
Extra payments work by immediately shrinking the balance that next month's interest is calculated on — every dollar of extra principal paid today is a dollar that never accrues interest again for the rest of the loan. That compounding effect is why a relatively small $100/month addition returns more than double its own annual cost in interest savings over the life of this loan. If your loan has no prepayment penalty (true for all federal loans and most private ones), extra payments toward principal are one of the most reliable ways to reduce total cost.
Related calculators
- Loan Calculator — a general-purpose version of this same amortization math.
- Debt Payoff Calculator — plan payoff across student loans and other debts together.
- Debt Consolidation Calculator — see if combining loans at a new rate helps or hurts.