Student Debt Calculator
Model multiple fixed-rate loans, extra monthly payments, interest savings and a month-by-month payoff schedule.
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How to use the student debt calculator
Each block explains one part of how this works and how to read the result.
Choose your method and enter inputs
Model multiple fixed-rate loans, extra monthly payments, interest savings and a month-by-month payoff schedule.
Enter each loan's principal, APR, term in months and optional extra monthly payment. Use the rate from your own loan documents and choose the calculation start date.
Formula and methodology
M = P x r / (1 - (1+r)^(-n)). At zero interest, M = P/n. Extra payments reduce the balance after interest.
The calculation breakdown lists what was counted and which rules were applied. Data-backed results identify their source and version; changing inputs clears a previous result so it cannot be mistaken for a new calculation.
Worked example
A $12,000 loan at 5.5% APR over 120 months has a standard monthly payment of about $130.23. Extra payments reduce the repayment term and interest.
Assumptions and limitations
Monthly fixed-rate amortization does not model federal daily interest, deferment, fees, capitalization or income-driven plans.
Check the result's method and linked source. A practice profile or planning estimate should be interpreted within its stated assumptions.
Frequently asked questions
How does the student debt calculator calculate its result?
M = P x r / (1 - (1+r)^(-n)). At zero interest, M = P/n. Extra payments reduce the balance after interest.
Can I use this without an account?
Yes. The tool is free and does not require a login. Financial worksheets calculate in your browser; DOI metadata is retrieved from Crossref.
What assumptions should I check?
Monthly fixed-rate amortization does not model federal daily interest, deferment, fees, capitalization or income-driven plans.
Can I access the same calculation through an API?
Yes. Use /api/tools/student-debt-calculator. Structured arrays and financial inputs use a JSON POST body. The API returns calculation steps and source provenance.
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Developer API
POST JSON to /api/tools/student-debt-calculator. The browser and API share the same deterministic engine. Financial inputs use POST only and responses are not cached. The service does not store your financial inputs.
Response fields: title, value, metrics, steps, rows, warnings, provenance. Citation responses also include normalized metadata and in-text citations.
Example JSON request
{
"startDate": "2026-10-08",
"loans": [
{
"name": "Loan A",
"principal": 12000,
"apr": 5.5,
"months": 120,
"extra": 0
},
{
"name": "Loan B",
"principal": 8500,
"apr": 6.2,
"months": 120,
"extra": 0
}
]
}
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