Debt Payoff & Credit

Debt is the most expensive drag on a savings rate. A credit card at 20% APR costs more than almost any investment returns, which is why paying down high-interest debt is the highest-return move most people can make. These calculators show you the exact cost of your debt, how fast different payoff strategies work, and what refinancing would save you.

Debt is the most expensive drag on a savings rate. A credit card at 20% APR costs more than almost any investment returns, which is why paying down high-interest debt is the highest-return move most people can make. This category covers the calculators that quantify your debt, compare payoff strategies, and show what refinancing saves.

The math behind the debt calculators

Every calculator here runs on the same two formulas: monthly amortization and compound interest.

Minimum payment amortization. The months to pay off a balance at a fixed payment is:

n = -ln(1 - r × P / M) / ln(1 + r)

where r is the monthly rate (APR ÷ 12), P is the balance, and M is the monthly payment. If M is less than or equal to r × P, the payment only covers interest and the balance never decreases.

Snowball vs avalanche. The debt snowball orders debts from smallest balance to largest, so you close accounts fast and build momentum. The debt avalanche orders from highest APR to lowest, which minimizes total interest. Both allocate the same monthly budget; they only differ in order. Avalanche is mathematically cheaper; snowball is psychologically stickier.

Debt-to-income. DTI is your total monthly debt payments divided by gross monthly income. Conventional mortgage lenders cap it at 43%; many prefer 36% or below.

Which calculator should you use?

• Carry a credit card balance? Start with the Credit Card Payoff Calculator. It shows the exact months and total interest for your current payment, and how extra payments shorten the timeline.
• Comparing payoff strategies? The Debt Snowball and Debt Avalanche calculators both show a month-by-month schedule. Run both with the same debts and budget, and compare total interest.
• Refinancing student loans? The Student Loan Refinance Calculator compares your current payment and total cost against a new rate and term.
• About to apply for a mortgage? Check your Debt-to-Income Ratio first, because it is the number lenders use to approve or deny.
• Considering a balance transfer? The Balance Transfer Calculator shows whether the 0% intro period and transfer fee beat keeping the card as-is.

The sequence that works

For most people, the order of operations is: build a small emergency buffer, then attack any debt above 6-8% APR, then invest. The interest you stop paying is a guaranteed return, and there is no investment that reliably beats paying off a 20% credit card. Once high-interest debt is gone, the freed-up payment rolls straight into savings, and your savings rate jumps without earning a single extra dollar.

Run these calculators with your real numbers, not aspirational ones, and revisit them every time your income or balances change.

Key Takeaways

• A 20% APR credit card doubles your balance in roughly 3.5 years at minimum payments
• The debt avalanche (highest APR first) saves the most money; the snowball (smallest balance first) builds momentum fastest
• A debt-to-income ratio over 43% blocks most conventional mortgages
• Student loan refinancing saves the most when you shorten the term, not just lower the rate
• Every dollar of extra payment goes straight to principal, cutting both months and total interest

Methodology: Debt calculations use standard amortization and compound-interest formulas: monthly rate = APR / 12; minimum payment amortization uses n = -ln(1 - r*P/M) / ln(1 + r). Snowball orders debts by smallest balance; avalanche orders by highest APR. All figures are estimates for educational purposes and vary by lender.

Who this category is for:

If you carry a credit card balance, start with the Credit Card Payoff Calculator to see how long it takes. Comparing strategies? The Debt Snowball and Debt Avalanche calculators show which order pays off your debts fastest. Buying a home or refinancing? Check the Debt-to-Income Ratio and Student Loan Refinance calculators first.

Is it better to pay off debt or invest?

Pay off any debt above roughly 6-8% APR before investing beyond your employer match, because the guaranteed interest you stop paying beats expected market returns at that level. Lower-rate debt like a sub-4% mortgage can reasonably be carried while investing. The debt calculators show the exact cost of carrying each balance.

What is a good debt-to-income ratio?

For a conventional mortgage, lenders want a DTI under 43%, and many prefer under 36%. The ratio is your total monthly debt payments divided by gross monthly income. Above 43%, most mortgage applications are denied or require a compensating factor.

How does a credit card balance grow?

Interest is charged monthly on the outstanding balance at APR/12. At 20% APR with minimum payments, a balance roughly doubles in about 3.5 years and can take decades to pay off. The payoff calculator shows the exact months and total interest for your numbers.

Should I refinance my student loans?

Refinancing helps when your credit improved or rates dropped enough to justify fees and losing federal protections. The refinance calculator compares current vs new payment and total cost over the term. Never refinance federal loans for private ones if you rely on income-driven repayment or forgiveness.

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