Student Loan Repayment and Extra-Payment Calculator
Compare standard payments with extra payments across multiple federal or private student loans.
What this calculator explains
A fixed-rate student loan can be modeled with standard amortization, but federal repayment plans, subsidies, forgiveness rules and borrower protections depend on current policy. This page focuses on transparent balance, payment and interest scenarios and directs users to Federal Student Aid for official eligibility and plan decisions.
Multiple-loan mode preserves each balance and interest rate so users can compare extra payments directed to the highest rate, the smallest balance or all loans proportionally. The result also explains that servicer allocation rules and accrued interest can affect a real payoff quote.
How the estimate is calculated
- Calculate the scheduled amortizing payment for each balance, rate and remaining term.
- Accrue monthly interest and apply the required payment.
- Allocate extra payment according to the user’s selected strategy.
- Apply one-time payments on the specified month.
- Continue until all balances are paid and calculate total interest.
- Compare the baseline with the extra-payment scenario.
Formula
Fixed monthly payment = P × r(1+r)^n ÷ ((1+r)^n − 1); extra principal reduces future interest when properly applied
Worked example
A $40,000 loan at 6.5% over 10 years has an estimated payment of $454.19 per month and about $14,503 of total interest. Adding $100 per month in this simplified model pays the loan in about 92 months instead of 120 and reduces estimated interest to roughly $10,871, a saving of about $3,632.
Current rules and configuration notes
- Fixed-rate loans use standard amortization; extra amounts reduce principal only when applied that way by the servicer.
- Federal income-driven repayment, forgiveness and eligibility outcomes must be referred to the official Federal Student Aid tools.
- Multiple-loan mode preserves each balance and rate so payoff ordering can be compared transparently.
Update requirement: Keep the amortization engine stable, but review federal-plan disclaimers and official StudentAid links whenever policy changes.
Included in the estimate
- One or multiple fixed-rate loans
- Scheduled payment and total interest
- Extra monthly and lump-sum payments
- Alternative extra-payment allocation strategies
- Payoff date and downloadable schedule
- Federal Student Aid referral for current official plan modeling
Not included or not guaranteed
- Current federal income-driven plan eligibility or payment certification
- Forgiveness, subsidy or tax treatment predictions
- Variable-rate changes unless a scenario is entered
- Servicer-specific payment allocation
- A lender or servicer payoff quote
Frequently asked questions
Can this calculate federal income-driven repayment?
Toolistify does not hardcode unstable federal eligibility and forgiveness rules. Use the official Federal Student Aid calculator for current income-driven and forgiveness scenarios.
Does extra payment always go to principal?
Interest due is generally satisfied first, and servicer practices can differ. Borrowers should confirm how to direct extra amounts and whether paid-ahead status is applied.
Which loan should receive extra payment first?
Targeting the highest rate generally minimizes interest, while targeting the smallest balance may close an account earlier.
Why is my payment different from the servicer amount?
Accrued interest, fees, capitalization, daily interest and plan-specific rules can create differences.
Can I include private and federal loans together?
Yes for a balance-and-interest comparison, but keep them labeled because protections and repayment options can differ.
Should I refinance federal student loans?
Refinancing can replace federal benefits with a private loan. This calculator compares entered cash flows but does not recommend giving up federal protections.
Official sources
Applicable period: 2026 · Last reviewed: September 3, 2026
Display the applicable period and a real Last reviewed date beside this source list.
Recommended internal links
See what an extra payment changes
Compare $25, $50, $100 and one-time-payment scenarios without changing the baseline loan.
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