Compound Debt Calculator
Compound interest is the engine of wealth when you invest. Point it at a debt and it runs the same engine in reverse, quietly manufacturing interest on top of interest while you look the other way. This compound debt calculator shows both directions at once: what your debt costs if you pay it down, and what it becomes if you leave it alone.
The payoff model uses standard monthly amortization: one interest charge per month at APR divided by 12. Real issuers usually compute interest on the average daily balance, so your statement may differ by a few dollars. The verdict bands are this calculator’s own reading, not a lender rule.
Quick Answer
A $6,000 balance at 22% APR with $200 monthly payments takes 44 months to clear and costs $2,791 in interest, for $8,791 total. Ignore the same balance for 5 years and compounding turns it into $17,846: nearly triple, with no payments made at all. At 22%, unpaid debt doubles roughly every 3.3 years by the rule of 72, an approximation, not the exact figure.
Key takeaways
- Compounding is directionless. The same math that grows savings grows debt: interest charged on interest, month after month.
- Minimums are mostly interest. On a $3,500 balance at 22%, about $64 of a $70 minimum is interest in month one: only $6 touches the principal.
- Below the interest line, debt never dies. If your payment is smaller than the monthly interest charge, the balance grows forever.
- Speed is the antidote. Every extra dollar of payment kills future interest, because interest is always charged on a shrinking balance.
- The verdict bands (25% and 40% interest share) are this calculator’s own reading of the result, not a lender threshold or a credit rule.
- Quick Answer
- How to use the compound debt calculator
- Compounding works against you exactly like it works for you
- Why minimum payments feel like treading water
- What a bigger payment actually saves
- Avalanche or snowball: picking a payoff order
- What competing calculators get wrong
- Three ways to break the compounding
- Frequently asked questions
- Add This Calculator to Your Website
- References
How to use the compound debt calculator
Enter three numbers and read both directions of the story: the payoff path and the left-alone path. The results stay hidden until you calculate.
- Enter the debt balance: what you owe right now. The worked example has $6,000 pre-filled.
- Enter the APR: the annual rate from your statement. The example uses 22%, close to the average rate on accounts actually assessed interest in the Federal Reserve’s G.19 data for 2026.
- Enter the monthly payment: the fixed amount you will pay every month. The example uses $200.
- Click Calculate Both Ways: the headline shows total interest, the sub-line shows payoff time and total paid, and the three boxes show time to debt-free, the 5-year left-alone balance, and the doubling time.
Blank or negative entries are treated as zero by the tool, not rejected: a zero balance reads as already paid off, and a zero payment on a positive balance reads as never paying off. If the result says “N/A”, your payment does not cover the monthly interest charge, and no payoff date exists at that payment.
Compounding works against you exactly like it works for you
Each month the tool multiplies your balance by the monthly periodic rate (APR divided by 12). Your payment covers that interest first; only the remainder reduces the balance. Leave the debt alone and the process runs in reverse: interest gets added to the balance, and next month’s interest is charged on the bigger number.
$8,791 total paid
$17,846 owed
The same $6,000 costs $8,791 with steady payments or balloons to $17,846 ignored. The $9,055 gap is the price of doing nothing, manufactured entirely by compounding. To see how the balance affects your borrowing capacity, check our debt-to-income ratio calculator.
Why minimum payments feel like treading water
The first month of a payoff is the worst month, because the balance is at its largest and the interest charge is at its largest too. That is why a minimum payment can feel like nothing is happening: most of it is interest, and the principal barely moves.
of a $70 first payment is interest on a $3,500 balance at 22%: $6 hits principal
first-month interest on the $6,000 example: over half of a $200 payment
doubling time of unpaid debt at 22% by the rule of 72 (exact monthly-compounding figure: about 3.2 years)
pays off when the payment is at or below the monthly interest charge
Most issuers compute interest daily on the average daily balance, as the Consumer Financial Protection Bureau explains, so paying earlier in the cycle also trims the charge slightly. This tool uses the simpler monthly model, which keeps the payoff math transparent at the cost of a few dollars of difference against a real statement. Grace periods only help if you pay the balance in full each month; once you carry a balance, new purchases start accruing interest immediately.
What a bigger payment actually saves
Every row below is the same $6,000 balance at 22% APR, run through this calculator at a different fixed payment. The pattern is the whole argument for paying more than the minimum: the payment rises in small steps, but the interest falls off a cliff.
| Monthly payment | Time to debt-free | Total interest | Total paid | Interest share |
|---|---|---|---|---|
| $120 | 137 months | $10,414 | $16,414 | 63% |
| $150 | 73 months | $4,913 | $10,913 | 45% |
| $200 | 44 months | $2,791 | $8,791 | 32% |
| $250 | 32 months | $1,979 | $7,979 | 25% |
| $300 | 26 months | $1,543 | $7,543 | 20% |
| $400 | 18 months | $1,081 | $7,081 | 15% |
Moving from $120 to $200 a month cuts the interest bill by more than $7,600 and clears the debt more than seven years sooner. That is the leverage a fixed payment has over a shrinking minimum, which drops as the balance drops and stretches the payoff out. Note the $120 row sits just above the interest line: the first month’s interest is $110, so only $10 of that payment reaches principal, and the payoff drags on for 137 months.
Avalanche or snowball: picking a payoff order
With one debt, the strategy is simple: pay as much as you can. With several, two schools compete. The avalanche method attacks the highest-APR balance first and is mathematically cheapest. The snowball method clears the smallest balance first for quick motivational wins. Avalanche saves more interest; the best method is the one you will actually stick with. Either way, run each balance through this calculator first to see its own interest line, then use our debt roll-up calculator to order several debts, or our early debt payoff calculator to test extra payments on one of them. If a consolidation loan is on the table, our credit card debt consolidation calculator compares the loan against your current payments.
What competing calculators get wrong
Most payoff tools answer only half the question. They show the payoff path and stop, leaving the reader to guess what happens if the debt is ignored, which is exactly the scenario that scares people into acting. Several use a single constant APR and never mention that real issuers compound daily on the average daily balance, which makes their “exact” schedules fiction by a few dollars a month. Others happily accept a payment below the monthly interest charge and report a payoff date anyway, instead of warning you the debt never clears. A few ignore fees, cash advances, and penalty APRs entirely without listing those exclusions. This calculator warns when the payment cannot cover interest, states its monthly model plainly, shows the unpaid-growth scenario most competitors leave out, and labels its verdict bands as its own reading rather than dressing them up as lender rules.
Three ways to break the compounding
Breaking the cycle is less about willpower than about beating one number: the monthly interest charge. Everything below works because it attacks that number directly.
- Beat the interest line first. Your payment must exceed balance times APR divided by 12 before a single dollar reduces the debt. Anything below that is just renting the balance.
- Consider a 0% balance transfer. Moving the balance to a promotional 0% card stops the compounding clock for the promotional window, commonly 12 to 21 months. The transfer fee, typically 3 to 5% of the balance, is usually far cheaper than months of interest, but only if you stop charging the new card.
- Automate a payment above the minimum. A fixed payment beats a percentage minimum because it does not shrink as the balance shrinks. Raising the payment even slightly shortens the payoff dramatically, because more of each payment reaches the principal. If the debt is already in collections, check what interest is accruing with our debt collection interest calculator.
Frequently asked questions
At 22% APR, a $6,000 balance left alone becomes $7,462 in one year, $11,540 in three years, and $17,846 in five years. The rule of 72 says it doubles about every 3.3 years, which is an approximation; the exact monthly-compounding figure at 22% is about 3.2 years.
Because the payment covers interest first. On a $3,500 balance at 22%, about $64 of a $70 minimum is interest, leaving $6 of principal reduction per month. As the balance falls, a percentage-based minimum falls too, which stretches the payoff further.
Yes, when the payment is at or below the monthly interest charge. Then the balance grows instead of shrinking, and no payoff date exists. The calculator shows N/A for total interest and warns that the payment does not cover the monthly interest.
Most issuers charge daily using the average daily balance method: each day’s closing balance times the daily periodic rate (APR divided by 365), summed over the cycle. This calculator uses one monthly charge at APR divided by 12 instead, so a real statement may differ by a few dollars.
Avalanche (highest APR first) is mathematically cheapest; snowball (smallest balance first) gives faster wins. The best method is the one you will stick with. Run each balance through this calculator first, then order them with a multi-debt tool.
Often, yes: a 0% promotional APR for 12 to 21 months pauses compounding, and the typical 3 to 5% fee beats months of interest at 22%. It backfires if you keep charging the new card, because the new spending accrues at the regular rate.
It is this calculator’s own reading of how much of your total payment goes to interest: under 25% reads as Manageable, 25% to under 40% reads as Expensive debt, and 40% or more reads as Interest is eating the payments. The bands are a planning aid, not a lender rule or a credit threshold.
Yes. It runs entirely in your browser, needs no account, and stores nothing. Copy the result with Copy my results or send it to another app with Share results.
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References
- Consumer Financial Protection Bureau. How does my credit card company calculate the amount of interest I owe? (average daily balance, grace periods). Accessed October 24, 2026.
- Consumer Financial Protection Bureau. What is a grace period for a credit card? (grace period lost once a balance is carried). Accessed October 24, 2026.
- Consumer Financial Protection Bureau. The Consumer Credit Card Market, report to Congress, December 2025 (interest assessed, minimum-only payers, APR levels). Accessed October 24, 2026.
- Consumer Financial Protection Bureau. Regulation Z, Section 1026.7: Periodic statement (minimum payment warning and 36-month repayment disclosures). Accessed October 24, 2026.
- Consumer Financial Protection Bureau. Regulation Z, Appendix M1: Repayment Disclosures (minimum-payment repayment estimate assumptions, including the average daily balance method). Accessed October 24, 2026.
- Consumer Financial Protection Bureau. Credit card contract definitions (grace period, due date, default). Accessed October 24, 2026.
- Board of Governors of the Federal Reserve System. Consumer Credit, G.19 (average credit card APRs, all accounts and accounts assessed interest). Accessed October 24, 2026.
- Board of Governors of the Federal Reserve System. Regulation Z, Section 1026.7: Periodic statement (repayment disclosure requirements). Accessed October 24, 2026.
- Cornell Law Institute. 12 CFR 1026.7: Periodic statement (minimum payment warning text and repayment estimates). Accessed October 24, 2026.
- Federal Reserve Bank of New York. Household Debt and Credit Report, Second Quarter 2026 (credit card balances of $1.26 trillion). Accessed October 24, 2026.