Debt Payoff Calculator

Extra payments buy time and reduce interest

Debt payoff math is simple but powerful: interest is charged on your remaining balance, so reducing the balance faster reduces future interest. That’s why extra monthly payments can have an outsized impact on total interest and payoff time.

This calculator models a blended debt balance with an average APR. That’s a useful approximation when you want a high-level plan. If you have multiple debts with different rates, you can still use a weighted average APR to understand the overall sensitivity to payment amount.

Use this tool to compare a baseline plan to an “extra payment” plan. The difference in total interest is a concrete way to measure the value of increasing your payment.

Why “average APR” is a planning shortcut

If you have multiple debts, each balance accrues interest at its own rate. The true payoff path depends on how you allocate payments across accounts. Modeling the full strategy (snowball vs. avalanche) requires account-level data and payment rules.

An average APR model is still useful when you want a quick answer to “what happens if I pay $X more per month?” A reasonable approach is to estimate a weighted average APR (higher weight for larger balances). The goal is not perfect precision; it’s understanding how sensitive your timeline is to payment level.

Three levers that change payoff time

There are only three levers: balance, APR, and payment. Reducing balance (through a lump sum or budgeting) and reducing APR (refinance, consolidation, balance transfer) can both accelerate payoff. Increasing payment is often the most direct lever.

Use this calculator to test combinations. For example, a modest APR reduction paired with a modest payment increase can outperform an aggressive payment increase alone. Seeing the numbers can help you choose the most realistic plan you can stick to.

Building a payoff plan you can maintain

The best payoff plan is one you can maintain for months, not days. If you choose an aggressive payment that forces you to use credit again, the plan can backfire. Leave room for essentials and a small emergency buffer.

If your income varies, consider setting a baseline payment you can always make, and add “extra” payments when income is higher. The calculator’s extra payment input helps you see what those extra months can do over time.

Limitations (and when you need a detailed model)

Because this calculator models a blended balance, it will not perfectly match a multi-debt plan where you allocate payments account by account. If you are choosing between snowball and avalanche, or if you have promotional rates, you may want an account-level schedule.

Still, the blended model is useful for understanding “big levers” and prioritizing actions: increasing payment, reducing APR, and reducing balance. Those levers improve payoff outcomes under almost any detailed strategy.

As a next step, once you have a payment target you can sustain, translate it into an account-by-account plan (minimums plus targeted extra payments). That’s where strategy selection matters most.