Student Loan Payment Calculator: Compare Loan Costs

This student loan payment calculator estimates the monthly payment and total interest for a fixed-rate loan when you enter its amount, annual percentage rate (APR), and term. Use it to compare the arithmetic of different loan scenarios; it does not determine eligibility, program benefits, or which borrowing option to choose.

Formula

The calculator uses the standard fixed-payment amortization formula. Monthly payment = principal × monthly rate ÷ [1 − (1 + monthly rate)^{−number of payments}]. In symbols, M = P × r / [1 − (1 + r)⁻ⁿ], where:

• P is the loan principal in dollars.
• r is the monthly interest rate as a decimal, calculated as APR ÷ 1,200.
• n is the number of monthly payments, calculated as years × 12.
• M is the monthly payment in dollars.

Total interest is calculated as M × n − P. Because the displayed payment is rounded to cents, the interest estimate uses that rounded payment. Actual final payments can differ slightly if a lender adjusts the last installment or calculates interest using different dates or conventions.

Worked Example

Using the defaults, the loan principal is $20,000, APR is 8%, and term is 5 years.

1. Convert APR to a monthly decimal rate: 8 ÷ 1,200 = 0.0066667.
2. Convert the term to payments: 5 × 12 = 60 monthly payments.
3. Substitute into the payment formula: $20,000 × 0.0066667 ÷ [1 − (1.0066667)⁻⁶⁰] = $405.53 per month, rounded to cents.
4. Calculate total interest using the displayed payment: $405.53 × 60 − $20,000 = $4,331.80.

The calculator therefore displays a monthly payment of $405.53 and estimated total interest of $4,331.80.

Assumptions

• The interest rate stays fixed for the full term.
• Payments are equal, made monthly, and begin after one month.
• Interest compounds monthly at APR ÷ 12.
• The estimate excludes fees, taxes, insurance, deferment, missed or extra payments, and any changes to the balance or rate.

How to Compare Student Loan Options

For a like-for-like arithmetic comparison, enter each loan’s principal, APR, and repayment term separately. Keep the other inputs constant when you want to isolate one factor. For example, comparing two APRs with the same $20,000 principal and five-year term shows how the rate alone changes the estimated payment and interest. Comparing two terms at the same APR illustrates the trade-off between payment size and the time interest accrues.

• Principal: Use the amount actually borrowed, not the total cost of attendance or an amount that includes grants and scholarships.
• APR: Enter the lender’s quoted annual percentage rate as a percentage, such as 8 for 8%. Ask the lender which rate and fees its disclosure includes.
• Repayment term: Enter years, not months. A 10-year term is 10; a 120-month term is also 10 years.
• Payment and interest: Compare both outputs. A smaller payment can result from extending the term while increasing total interest.

Student borrowing options may differ in more than their payment math. Depending on the specific loan, terms can include fixed or variable interest, fees, repayment conditions, deferment provisions, or borrower protections. This calculator does not model those features. Review the actual written disclosures and ask the loan servicer or provider how each feature applies; do not assume two loans with identical APRs and terms otherwise work alike.

What This Estimate Leaves Out

This is an amortization estimate for a single loan with a fixed rate and regular monthly payments. It cannot determine whether a loan is federal or private, assess program eligibility, or calculate benefits or consequences under a repayment, forgiveness, or tax program. Program and servicing rules can change and depend on individual circumstances; check current details with the relevant servicer or program rather than treating this calculator as a rules guide.

The calculation also assumes the full principal accrues interest under the same rate from the start of repayment. It does not account for interest that accumulates before repayment, capitalization, a grace period, payment pauses, income-based payment changes, variable rates, fees added to the balance, or extra payments. If any of these apply, the actual balance and payment schedule may differ. For a more useful comparison, obtain the lender’s payment schedule and confirm the balance and rate on which it is based.

A common misconception is that a low monthly payment necessarily means a lower-cost loan. It may simply reflect a longer term: payments are spread over more months, so interest can accumulate for longer. Conversely, shortening a term generally raises the scheduled payment in this fixed-rate formula while reducing the number of interest-accruing months. The calculator compares these mathematical effects, not whether a payment fits a household budget or whether a borrower will qualify.

Using the Results Carefully

Enter the amount and terms from an actual offer when available, and keep units consistent. APR is entered as a percentage, while the formula converts it to a monthly decimal. The term is in years. A rounding difference of a few cents—or a different final installment—can occur because lenders may use daily interest, different payment dates, fees, or other contract terms. If a quoted payment differs, compare the disclosure’s assumptions before drawing conclusions.

For multiple loans, calculate each one separately rather than combining balances with different rates or terms into a single entry. A combined estimate can conceal which loan drives the cost and may not represent the actual repayment schedule. Save each scenario’s inputs alongside its result so that comparisons remain clear.

Frequently Asked Questions

How do I compare two student loans?
Enter each loan’s principal, APR, and term, then compare estimated monthly payment and total interest. Also review each loan’s fees, rate type, repayment conditions, and other contractual terms separately.

Does a longer student loan term lower the monthly payment?
For the same principal and fixed APR, this formula generally produces a lower monthly payment over a longer term. The total interest estimate can increase because payments continue for more months.

Does this calculator include fees or interest during school?
No. It models a fixed-rate balance repaid in equal monthly installments and excludes fees and interest that may accrue before repayment. Use the actual repayment balance and lender schedule for a closer estimate.

Can I use it for a variable-rate loan?
Only as a simplified snapshot using one APR. A variable rate can change, so payments and total interest may differ from this fixed-rate estimate.

Does the result tell me which loan to take?
No. It compares payment arithmetic only and does not assess eligibility, protections, program rules, personal finances, or the full terms of an offer.

This result is an estimate, and the lender’s disclosure gives the exact figures.

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in p | Loan amount | $ | 20000 | 1 | 100000000
in apr | Interest rate (APR) | % | 8 | 0.01 | 100
in yrs | Loan term | years | 5 | 0.0833 | 50
out pmt | Monthly payment | $ | p * (apr / 1200) / (1 - (1 + apr / 1200) ^ -(yrs * 12)) | 2
out int | Total interest | $ | pmt * yrs * 12 - p | 2