The math behind minimum payments (and why balances stick)
Minimum payments mostly cover interest on high-APR balances, leaving little for principal. When your payment is at or below the monthly interest charge, the balance grows even if you pay every month. Our payoff tools flag this as 'never pays off' — fix the payment before debating snowball vs avalanche.
How monthly interest is calculated
Most revolving accounts use a daily periodic rate derived from the APR. For planning, monthly interest ≈ balance × (APR ÷ 12). On a $8,000 balance at 20% APR, monthly interest is about $133 before any principal reduction.
If your minimum payment is $150, only about $17 goes to principal that month. At that pace payoff takes years and total interest is large — enter your numbers in the planner to see the exact timeline.
Monthly interest ≈ balance × (APR ÷ 12) Principal reduction = payment − interest − fees
When the balance never shrinks
If payment ≤ monthly interest, the balance grows. Our calculators return null months-to-payoff in that case. The fix is raising the payment, not switching payoff order.
Promotional 0% periods end. When the APR jumps, the same minimum may suddenly fail to cover interest. Recalculate when promotional rates expire.
| Balance | APR | Approx. monthly interest | Payment that fails |
|---|---|---|---|
| $5,000 | 24% | $100 | $100 or less |
| $10,000 | 18% | $150 | $150 or less |
| $3,000 | 29% | $72.50 | $72 or less |
What to do next
Increase payment on the account where payment barely exceeds interest. Even $25 more can move the payoff date.
Use avalanche ordering if you carry multiple debts — it attacks the highest APR first.
If you cannot raise payments, read when-the-plan-does-not-work for honest options that do not pretend approval is likely today.
Putting this into practice
Issuer minimums often drop as balances fall, which feels like progress while interest still dominates. Compare principal reduction dollars, not just the minimum due on the statement.
Multiple small minimums across many cards can hide that one account is growing. Run the audit worksheet on every open revolving account, not only the largest balance.
If every account passes the interest test but progress still feels slow, the lever is extra payment — not a different payoff order.
When a promotional rate ends, recalculate immediately — the same dollar minimum can flip from workable to never pays off overnight.
Use the comparison table above as a sanity check: if your payment is near the failing column, add at least enough to clear monthly interest plus one dollar of principal.
Frequently asked questions
- Why did my minimum payment go up?
- Issuers often set minimums as a percentage of balance. As balance grows, minimum grows — but may still not cover interest on high APRs.
- Does paying twice a month help?
- More frequent payments can reduce average daily balance on some accounts, which slightly lowers interest. The bigger lever is paying more total per month.
- Should I only pay minimums on some cards?
- In a structured plan you pay minimums on all but the target debt. Paying only minimums everywhere with no extra means the slowest possible payoff and often never pays off high-APR balances.
Related tools
Save or print this guide
Printable: Minimum payment audit worksheet
- For each card: balance, APR, minimum payment
- Calculate monthly interest = balance × (APR ÷ 12)
- Flag accounts where payment ≤ monthly interest
- Raise payment on flagged accounts first
- Re-run planner after changes
- Set alert before promotional 0% periods end
- Track principal reduction dollars, not just lower minimums