Debt Payoff Calculator

Every extra dollar you put toward debt saves you more than a dollar in future interest — and gets you to debt-free faster. This calculator shows exactly how long it takes to pay off a single debt, how much total interest you'll pay, and how dramatically extra monthly payments change both numbers.

Enter Your Measurements

Current Balance($)

Annual Interest Rate (APR)(%)

Check your credit card or loan statement for your APR

Monthly Payment($)

Must exceed the minimum interest charge to make progress

Extra Monthly Payment($)

Additional amount beyond your regular payment

Results

Months to Pay Off (current payment)

months

Total Interest (current payment)

3,524

Months to Pay Off (with extra payment)

months

Interest Saved with Extra Payment

1,371

Months Saved

months

Formula

Monthly Interest = Balance × (APR / 12) Months to Payoff = -log(1 − (Balance × r / Payment)) / log(1 + r) where r = monthly rate (APR / 12)

How to Use This Calculator

How to Use

1
Enter your current debt balance.
2
Input your APR (annual percentage rate) from your statement.
3
Set your current monthly payment amount.
4
Add an extra payment amount to see how it changes your payoff timeline and total interest.

Frequently Asked Questions

What is the debt avalanche method?

The debt avalanche method means paying minimum payments on all debts, then putting all extra money toward the highest-interest debt first. Once that's paid off, you roll its payment to the next highest-rate debt. Mathematically, this minimizes total interest paid and is the most efficient approach. Compare it to the debt snowball method, which targets the smallest balance first for psychological momentum.

How much interest can I save with extra payments?

On a $8,000 credit card balance at 20% APR, making minimum payments (around $160/month) takes over 30 years and costs $14,000+ in interest. Paying $400/month instead pays it off in 26 months and costs only $1,800 in interest — saving $12,200. Even $50/month extra on a fixed payment dramatically shortens the timeline.

What's the difference between APR and interest rate?

APR (Annual Percentage Rate) includes the interest rate plus any fees. For credit cards, APR and interest rate are usually the same number. For mortgages and personal loans, APR is slightly higher than the stated rate because it factors in origination fees, points, and other costs. Always use APR when comparing loan costs.

Should I pay off debt or invest?

Compare your debt's interest rate to your expected investment return. High-interest debt (credit cards at 18–24%) should almost always be paid off first — it's essentially a guaranteed 18–24% return. Low-interest debt (mortgages at 3–6%) may be worth carrying while investing, especially if you have employer 401k matching to capture first.

Related Calculators

Compound Interest Calculator

Mortgage Calculator

Savings Goal Calculator

Retirement Savings Calculator

About This Calculator

This calculator uses the formula: Monthly Interest = Balance × (APR / 12) Months to Payoff = -log(1 − (Balance × r / Payment)) / log(1 + r) where r = monthly rate (APR / 12). All calculations follow industry-standard methods. Results are estimates — always verify with a licensed professional for structural or code-compliant work.

Built and maintained by the CalcSmart team. Last updated March 2026.

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