Student Loan Repayment Strategy Calculator

Student loan repayment strategy calculator for avalanche vs snowball

When you have more than one student loan, the question is not only “what is my monthly payment,” but “where should my extra money go first.” This student loan repayment strategy calculator compares three practical scenarios: paying only minimum payments, using the avalanche method, and using the snowball method. It estimates how long it takes to become debt-free and how much interest you pay along the way.

The two main strategies differ in what they prioritize. The avalanche strategy targets the highest interest rate first while you keep paying minimums on the other loans. This usually minimizes total interest paid. The snowball strategy targets the smallest balance first while you keep paying minimums on the other loans. This often produces faster “wins” because a loan can disappear earlier, which some people find easier to stick with. This calculator is built for the dominant real-world decision: you have a fixed monthly budget for your loans (minimums plus any extra), and you want to choose how to allocate that extra payment.

To use the calculator, enter each loan’s current balance, interest rate, and minimum monthly payment. You can enter up to five loans and leave unused rows blank. Then enter your extra monthly payment, if any. The results show payoff time and total interest for minimum-only, avalanche, and snowball, plus a simple comparison that highlights how much interest you can save by applying your extra payment strategically. If your inputs imply that your payments do not cover monthly interest, the calculator will stop and tell you why, because that scenario increases the balance over time.

Assumptions and how to use this calculator

• Interest is simulated monthly, using a monthly rate derived from your entered rate (APR percent by default).
• Minimum payments are paid first each month (until a loan is paid off), then any extra amount is allocated by the chosen strategy.
• If you enter 0 for a minimum payment, the calculator treats it as no required payment on that loan, which can cause negative amortization.
• The model does not apply fees, late charges, capitalization rules, grace periods, deferment, or income-driven repayment program rules.
• Extra payment is assumed to be available every month and constant; changing income or one-off lump sums are not modeled here.

Common questions

Which method is “best” for saving money?

If you can stick to the plan, avalanche is usually the lowest-interest option because it attacks the highest-rate debt first. The calculator shows total interest for both methods so you can see the size of the gap for your specific loans.

Why does the snowball method sometimes finish earlier?

Snowball can remove a small loan early, which frees up its minimum payment sooner. That larger combined payment can accelerate later loans. Depending on your balances, rates, and minimums, this can slightly reduce total months even if interest paid is higher.

What does “negative amortization” mean, and why would I see an error?

Negative amortization happens when your monthly payment is not enough to cover monthly interest. In that case the balance grows, so there is no meaningful payoff timeline. If the calculator detects this, increase the total payment (minimums or extra) or correct the inputs.

Do I enter interest as APR or a monthly rate?

Most people know APR, so the default assumes the rate you enter is APR percent and converts it to a monthly rate. If you already have a monthly interest rate, switch the advanced option to “Monthly rate percent” to avoid double conversion.

Does this apply to income-driven repayment plans or forgiveness programs?

No. This calculator is for standard repayment behavior where you control the allocation of your monthly payments across multiple loans. Income-driven plans, forgiveness rules, and changing payments depend on policy and personal circumstances and are not modeled here.