Numbers from this site's public API on a 5-card $40,000 portfolio at 15-24% APR. Open the calculator with your own balances and rates and the same numbers come out in real time.
The example portfolio
$40,000 is the size where the minimum payments alone cross $1,000 a month, and where a six-month deadline stops being a budgeting exercise and becomes a funding problem. This page uses five US credit cards — the same five-card shape as the $40K in 1 year case study, so the two pages can be read side by side. Card A carries $12,000 at 24% APR with a $300 minimum; Card B $9,000 at 21% with a $225 minimum; Card C $8,000 at 19% with a $200 minimum; Card D $6,500 at 17% with a $163 minimum; Card E $4,500 at 15% with a $112 minimum. The five minimums add up to $1,000 a month.
The rates run a ladder from 24% down to 15%, and the largest balance carries the highest rate — the shape where snowball and avalanche genuinely disagree. Weighted by balance, the portfolio's rate is 20.175% a year: $12,000 × 24%, $9,000 × 21%, $8,000 × 19%, $6,500 × 17% and $4,500 × 15% come to $8,070 of annual interest on a $40,000 balance. One twelfth of that is 1.68125%, which on the opening balance is $672.50 for the first month.
To clear all five in six months, the snowball method needs $7,425 a month, which is $6,425 above the minimums. Avalanche needs less — $7,339 — because it goes straight at the 24% card. Every figure on this page is for the snowball plan unless it says otherwise.
The deadline is a step, not a slope
Most payoff pages treat the monthly payment as a dial you turn up until the debt disappears, and the cost of a slightly smaller payment as a slightly longer schedule. On this portfolio that intuition is wrong at exactly one place, and that place is the deadline itself. $7,425 a month finishes the $40,000 in six months, with $2,510.83 of interest. $7,424 — one dollar less — takes seven months, with $2,511.18 of interest. The extra month costs 35 cents.
That is not a rounding artefact; it is what a deadline is. The seventh month exists because the sixth month ends a few dollars short, so the seventh payment is $4.18 — a leftover, not a month of work. Read the other way, it is the sharpest version of the usual advice: the last dollar you add to the payment is not buying interest relief, it is buying the calendar. Everything above the threshold is interest; everything at the threshold is the deadline.
| Payment | Method | Months | Interest | Extra month |
|---|---|---|---|---|
| $7,425 threshold | Snowball | 6 | $2,510.83 | — |
| $7,424 $1 less | Snowball | 7 | $2,511.18 | $0.35 |
| $7,339 threshold | Avalanche | 6 | $2,183.07 | — |
| $7,338 $1 less | Avalanche | 7 | $2,183.39 | $0.32 |
The step does not repeat itself further down. Between $7,424 and $6,500 the schedule stays at seven months and the interest climbs steadily — $2,511.18 at $7,424, $2,865.44 at $6,500 — and only at $6,000 does it step again, to eight months and $3,103.50. The staircase has long landings and short drops; the deadline is the top drop, and it is the cheapest one to avoid, because clearing it costs a dollar.
One thing about the plan payment is worth spelling out, because it is where the $2,039.17 sits. Only part of the $7,425 is fixed. The $6,425 of new money is fixed. The $1,000 of minimums bundled inside it is not: it is the sum of the minimums still owed on cards that carry a balance, so it narrows as each card is closed out. Card E is retired after month 1, Card D after month 2, Card C after month 3 and Card B after month 5, which pulls that floor down from $1,000 to $888, $725, $525, $525 and finally the $300 left on Card A. The six actual payments are therefore $7,425, $7,313, $7,150, $6,950, $6,950 and $6,722.83, and they add to $42,510.83 — $2,039.17 below the $44,550 that six flat $7,425 payments would total.
What the plan costs, and what the method is worth
On this portfolio the interest bill is $2,510.83 on the snowball method and $2,161.82 on the avalanche — both measured at the same $7,425 a month, so the two methods are compared at equal payment — a gap of $349.01, which is 13.90% of the interest bill. The avalanche row in the table above reads $2,183.07 instead, because that is avalanche at its own lower threshold of $7,339: the same six months, a smaller payment, and therefore a slightly bigger interest bill. Both are six-month figures — the only thing that differs is the payment each one is measured at. The total that leaves your account is $42,510.83, which is the $40,000 balance plus the interest, so the interest is 6.28% of the balance you started with and 5.91% of everything you send. Against a full year at the blended rate, the plan's $2,510.83 is 31.11% of the $8,070 an untouched $40,000 would be charged in twelve months.
What the method changes is the order the cards leave in. Snowball clears Card E in month 1, Card D in month 2, Card C in month 3, Card B in month 5 and Card A in month 6. Avalanche clears Card A in month 2, then Card B in month 4, Card C in month 5, and finishes Card D and Card E together in month 6. Both are debt-free at month 6, and avalanche gets there with $349.01 less interest — but the method is not the lever that moves this plan. The threshold is, and the threshold is set by the payment, not by the order.
The same six months, on minimums only
Sending $1,000 a month clears this portfolio in 82 months — close to seven years — and costs $28,678.10 in interest, a total bill of $68,678.10. The six-month plan's $2,510.83 is 8.76% of that, a saving of $26,167.27.
The same-term comparison is the sharper one, because both plans are spending the same six months. The minimums move $6,000 out of your account, of which $3,954.60 is interest and only $2,045.40 reaches principal, leaving $37,954.60 still owed. Six months of minimums therefore pay 1.58 times the interest the entire six-month plan costs — you can pay more interest in half a year than a working plan charges from start to finish, and the variable that decides which happens is the size of the payment.
Where the $6,425 comes from
This is the part that decides whether the plan happens, so it is worth stating plainly: you need $6,425 a month above the $1,000 you already pay, and over the six months that is $38,547.83 — 96.37% of the original balance. At $25 an hour after tax it is roughly 59 extra hours a week, which is a second income rather than extra shifts. At this size a six-month payoff is funded from the top of a short list — a vehicle, a second property or an inheritance turned into cash, a fixed-term contract, or a retirement-contribution pause above the match — and usually from more than one of them.
Two things soften it. The floor narrows on its own, so the plan payment is under $7,200 from month 3 without you changing anything, and the last payment is $6,722.83. And the deadline is a step in your favour as well: if you can only find $5,500 of new money instead of $6,425, the plan becomes a seven-month plan at $2,865.44 of interest rather than a failed six-month plan — and that is still a fraction of the $3,954.60 the minimums charge over the same six months.
Reproduce these numbers
Every figure on this page comes from this site's public API. Post the five balances, their rates, their minimums and extra: 6425 to /api/payoff and you get the same months, the same $2,510.83 and the same per-card breakdown. Two things that trip people up: APR goes in as a percentage (24, not 0.24), and extra is the amount above your total minimums, not your total payment — $6,425 here, which is what turns the $1,000 in minimums into $7,425 a month. Change extra to 6424 and the same run comes back with seven months, which is the whole point of this page. Or just open the calculator and type your balances in — same engine, no payload.
If your target is a different size or a different deadline, the same analysis is in the $40K in 1 year, $30K in 6 months, $20K in 6 months, $15K in 6 months, $10K in 6 months, $5K in 6 months, $5K in 1 year, $10K, $15K, $20K, $25K, $30K, $50K and $100K case studies, plus a 36-second walkthrough of the $25K case on YouTube. Shorter answers to the most common payoff questions live in the payoff questions hub.
Frequently asked
How much do I have to pay a month to clear $40,000 in six months?
On the five-card example here, $7,425 a month clears the $40,000 in six months on the snowball method, which is $6,425 above the $1,000 in minimums. Avalanche needs less — $7,339 — because it goes at the 24% card first. Both thresholds are exact, and they are steps rather than slopes: at $7,424 the snowball plan slips to seven months, and avalanche's own cliff is $7,338.
How much interest do I pay on $40,000 over six months?
$2,510.83 on the snowball method and $2,161.82 on the avalanche — both at the same $7,425 a month — a gap of $349.01 which is 13.90% of the interest bill. Avalanche at its own lower threshold of $7,339 is $2,183.07 for the same six months: a smaller payment, so a slightly bigger interest bill. The interest is 6.28% of the original $40,000 and 5.91% of everything that leaves your account. The total over the six months is $42,510.83 on snowball — the $40,000 balance plus $2,510.83 of interest.
What happens if I pay $1 less than the six-month payment?
You owe a seventh month. At $7,425 the snowball plan is finished in six months for $2,510.83 of interest. At $7,424 — one dollar less — the same portfolio takes seven months and the interest rises to $2,511.18, which is $0.35 more. The seventh payment is $4.18. The same cliff sits under the avalanche threshold: $7,339 clears it in six months for $2,183.07, and $7,338 takes seven months for $2,183.39, $0.32 more.
Why is the payment $7,425 in month 1 and less later on?
Because only part of it is fixed. The $6,425 of new money never moves, but the $1,000 of minimums bundled inside the payment is the sum of the minimums still owed on cards that carry a balance, and it narrows as cards are closed out — Card E after month 1, Card D after month 2, Card C after month 3 and Card B after month 5 — so the floor walks from $1,000 to $888, $725, $525, $525 and finally the $300 left on Card A. The six actual payments run $7,425, $7,313, $7,150, $6,950, $6,950 and $6,722.83, which adds to $42,510.83 — $2,039.17 below the $44,550 that six flat $7,425 payments would total.
Does snowball versus avalanche matter on $40,000 over six months?
It is worth $349.01 over the six months, which is 13.90% of the interest bill. Avalanche pays $2,161.82 and snowball pays $2,510.83, both at the same $7,425 a month. The payoff orders are genuinely different — snowball clears Card E, then Card D, then Card C, then Card B and finally Card A, while avalanche clears Card A first and finishes on Card D and Card E together in month 6 — but both methods reach zero in month 6. Avalanche simply gets there with a lower payment as well: its own threshold is $7,339 against the snowball's $7,425, and at that smaller payment the same six months cost $2,183.07.
What if I only pay the minimums on $40,000?
The $1,000 in minimums clears the balance in 82 months — close to seven years — and costs $28,678.10 in interest, a total bill of $68,678.10. Over the same six months the minimums move $6,000 out of your account, pay $3,954.60 of interest and retire only $2,045.40 of principal, leaving $37,954.60 still owed. The six-month plan's $2,510.83 is 8.76% of the minimums-only interest, a saving of $26,167.27.
What is the blended interest rate on this portfolio?
20.175% a year, weighted by balance: $12,000 at 24%, $9,000 at 21%, $8,000 at 19%, $6,500 at 17% and $4,500 at 15% work out to $8,070 of annual interest on $40,000. One twelfth of that is 1.68125%, which is $672.50 on the opening balance — and $672.50 divided by $40,000 is exactly 20.175% divided by twelve. By month 6, under the plan, the monthly interest is down to $131.82.
How much new money do I have to find each month for a six-month $40,000 payoff?
$6,425 a month above the $1,000 you are already paying, which over the six months comes to $38,547.83 — 96.37% of the original balance. At $25 an hour after tax that is roughly 59 extra hours a week, so at this size the six-month payoff is funded from an asset sale, a windfall or a contract, not from trimming a budget.