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Student Loan with Fixed Monthly Repayment

Estimate a level monthly loan payment and total interest under a fixed-rate amortization model, including zero interest.

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Calculator inputs

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How to use this calculator

  1. Enter the known values in the units shown. Results update as you type.
  2. Where results are editable, change one to solve backwards. Lock a value to hold it fixed.
  3. Use the worked example to check the method. Reset restores the starting fields.

Use the result with context

Results are estimates for planning and education. Confirm rates, taxes, fees, and legal requirements with the relevant institution or a qualified professional before making a financial decision.

Formula and method

A balance of 1,200 repaid over twelve months at zero interest requires twelve payments of 100. Total paid is 1,200 and interest is zero.

Payment = principal × i/[1 − (1+i)^(−months)]; at i = 0, payment = principal/months

Worked example

Enter these known values and leave the other values blank.

Loan balance
1200 USD
Remaining repayment term
12 yrs / mos
Nominal annual interest rate
0 %
Level monthly payment
100 USD

Assumptions and limitations

  • Principal and term are positive, and the annual rate is nonnegative. The nominal annual rate is divided by twelve.
  • The model makes equal payments at the end of each month and amortizes the balance fully. It does not model daily accrual, variable rates, deferment, fees or income-based repayment rules.
  • The term should represent the intended number of monthly payments. Fractional terms produce a mathematical estimate rather than an actual dated payment schedule.
  • Payments retain full internal precision. Actual rounding can change the last payment and total interest.

Common questions

Does this include loan forgiveness or income-based payments?

No. It is a fixed-rate, level-payment amortization model. Program-specific repayment rules require a different calculation.

Can the rate be zero?

Yes. The payment becomes principal divided by the number of months, with zero interest.

References

Bookify requires payments above monthly interest to amortize principal in the level-payment model. Bookify evaluates the zero-interest limit directly, including available reverse calculations; nonzero-rate source expressions are preserved.

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