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Debt snowball — payoff time and interest
One debt, one payment: the calculator works out how many months it takes, what you pay in all, and how much of it is interest.
★ MONEY · DEBT · PAYOFF
Debt Snowball Calculator: Payoff Time & Interest 2026
An $8,000 debt at 19.99% APR with $350 a month takes 30 months to clear — 2 years and 6 months, $10,153.28 in all, $2,153.28 of it interest. Enter your balance, APR and monthly payment to work out your payoff time, your total paid and your interest — and see how the debt snowball orders your debts smallest first.
How the debt snowball works
The debt snowball is a payoff order, not a formula: list your debts from the smallest balance to the largest, pay the minimum on all of them, and throw every spare dollar at the smallest one until it is gone — then roll that whole payment onto the next smallest. The win is psychological: the smallest debt disappears first, and each payoff frees a payment for the next debt. This calculator works out one debt at a time, so you can price each step of the snowball.
The ordering example: a $500 store card, a $2,000 credit card and an $8,000 loan. The snowball order is 1. the $500 store card, 2. the $2,000 credit card, 3. the $8,000 loan — smallest balance first, whatever the APRs. Clear the $500 card first, then add its payment to the $2,000 card, then add both payments to the $8,000 loan. The avalanche method would order by APR instead; the snowball orders by balance, because a quick first win keeps people going.
The worked example, line by line
Defaults: balance $8,000, APR 19.99%, monthly payment $350.
Line 1 — the monthly rate. 19.99% ÷ 12 = 1.6658% a month, or 0.0166583. The first month’s interest is $8,000 × 0.0166583 = $133.27, so the payment must be above $133.27 or the balance never falls — $350 clears it by $216.73 a month at first.
Line 2 — the exact months. −ln(1 − $8,000 × 0.0166583 ÷ $350) ÷ ln(1 + 0.0166583) = −ln(0.61924) ÷ ln(1.0166583) = 0.47927 ÷ 0.0165211 = 29.01 months.
Line 3 — the whole months. 29.01 rounds up to 30 months — 2 years and 6 months — because a part-month still needs a payment. That is 29 full payments of $350.00 and one final payment.
Line 4 — the final payment. After 29 payments the balance is $3.22; one more month of interest makes the final payment $3.28. A tiny final payment is normal when the exact payoff lands just past a whole number of months.
Line 5 — the total paid. 29 × $350.00 + $3.28 = $10,153.28.
Line 6 — the interest. $10,153.28 − $8,000.00 = $2,153.28 — about 27% on top of the balance.
Every branch, checked
$250 a month: 47 months (3 yr 11 mo), total $11,524.36, interest $3,524.36. Paying $100 less a month costs 17 extra months and $1,371.08 of extra interest — the balance stays high longer, so interest compounds longer.
$500 a month: 19 months (1 yr 7 mo), total $9,381.87, interest $1,381.87. Paying $150 more a month saves 11 months and $771.41 of interest.
$5,000 balance: 17 months (1 yr 5 mo), total $5,758.33, interest $758.33 — $4,394.95 less in total than the $8,000 debt. A smaller balance clears far faster at the same payment — which is exactly why the snowball attacks the smallest debt first.
APR 12%: 27 months (2 yr 3 mo), total $9,128.36, interest $1,128.36. A rate nearly 8 points lower saves 3 months and $1,024.92 of interest on the same balance and payment.
APR 24.99%: 32 months (2 yr 8 mo), total $10,975.11, interest $2,975.11. A rate 5 points higher costs 2 extra months and $821.83 of extra interest.
Reverse — the payment a payoff date needs: $407.13 a month clears the $8,000 in 24 months; $741.04 a month clears it in 12 months; $297.27 a month clears it in 36 months. And $350 a month clears at most $6,877.46 in 24 months — a bigger balance needs a bigger payment or more time.
Output · formula · meaning
| Output | Formula | What it means |
|---|---|---|
| Months to pay off | ceil(−ln(1 − B×i÷P) ÷ ln(1+i)), i = APR÷12 | 30 months at the defaults (exact 29.01). |
| Years and months | months ÷ 12 | 2 yr 6 mo. |
| Total paid | (months − 1) × payment + final payment | $10,153.28. |
| Total interest | total paid − balance | $2,153.28. |
| Final payment | balance after months − 1 payments × (1+i) | $3.28. |
| First payment interest | balance × i | $133.27. |
| First payment principal | payment − first interest | $216.73. |
| $250 a month | same model, $250 | 47 months, $11,524.36 total, $3,524.36 interest. |
| $500 a month | same model, $500 | 19 months, $9,381.87 total, $1,381.87 interest. |
| $5,000 balance | same model, $5,000 | 17 months, $5,758.33 total, $758.33 interest. |
| APR 12% | same model, 12% | 27 months, $9,128.36 total, $1,128.36 interest. |
| APR 24.99% | same model, 24.99% | 32 months, $10,975.11 total, $2,975.11 interest. |
| Reverse: 24-month payoff | B×i ÷ (1 − (1+i)^−24) | $407.13 a month. |
| Reverse: 12-month payoff | B×i ÷ (1 − (1+i)^−12) | $741.04 a month. |
| Reverse: 36-month payoff | B×i ÷ (1 − (1+i)^−36) | $297.27 a month. |
| Reverse: max balance at $350/24 mo | P × (1 − (1+i)^−24) ÷ i | $6,877.46. |
Who uses this
- The cardholder with three debts: they learn the $500 store card goes first, then the $2,000 card, then the $8,000 loan — so they know the snowball order, and they check the $8,000 debt at 30 months and $2,153.28 of interest before they start.
- The borrower choosing a payment: they learn $250 a month takes 47 months and $3,524.36 of interest against 19 months and $1,381.87 at $500 — so they know a $250 swing is worth $2,142.49 of interest, and they check the $407.13 that clears it in 24 months.
- The borrower with a payoff deadline: they learn $741.04 a month clears the debt in 12 months and $297.27 in 36 months — so they know the payment their deadline needs, and they check the $6,877.46 that $350 a month can clear in 24 months.
- The borrower comparing rates: they learn 12% costs $1,128.36 of interest against $2,975.11 at 24.99% — so they know a balance transfer to a lower rate is worth real money, and they check the 27-month payoff at 12% against 32 months at 24.99%.
Accuracy & limitations
The math is exact for the numbers you enter: the months follow the payoff formula, the total is the full payments plus the final one, and the interest is the total minus the balance. What the model cannot do is read your statement for you: check the APR, because a card at 12% and a card at 24.99% give very different payoffs, and check whether new charges are being added — this calculator assumes the balance only shrinks. It assumes a fixed APR, the same payment every month, no fees, no late charges and no minimum-payment changes. It prices one debt at a time: the snowball itself is the order you attack them in, smallest balance first. For the avalanche comparison, see debt snowball vs debt avalanche; for a balance transfer, see balance transfer vs loan.
Cite this calculatorBright Side Kit. “Debt Snowball Calculator: Payoff Time & Interest 2026.” brightoolbox.com, 2026. Method: i = APR ÷ 12; months = ceil(−ln(1 − B×i÷P) ÷ ln(1+i)); total paid = (months − 1) × P + final payment; final payment = balance after months − 1 payments × (1+i); total interest = total paid − B. Defaults: balance $8,000, APR 19.99%, payment $350 → exact 29.01 months, 30 months (2 yr 6 mo), total paid $10,153.28, interest $2,153.28; final payment $3.28; first payment $133.27 interest and $216.73 principal; minimum payment to shrink the debt $133.27. Branches: $250/mo → 47 months, $11,524.36 total, $3,524.36 interest; $500/mo → 19 months, $9,381.87 total, $1,381.87 interest; $5,000 balance → 17 months, $5,758.33 total, $758.33 interest; APR 12% → 27 months, $9,128.36 total, $1,128.36 interest; APR 24.99% → 32 months, $10,975.11 total, $2,975.11 interest. Reverses: 24-month payoff → $407.13/mo; 12-month payoff → $741.04/mo; 36-month payoff → $297.27/mo; max balance at $350/24 mo → $6,877.46. Snowball order example: $500 store card, $2,000 credit card, $8,000 loan.
Bright Side Kit. "Debt Snowball Calculator: Payoff Time & Interest 2026." https://brightoolbox.com/debt-snowball-calculator/ Accessed October 25, 2026.Frequently asked questions
How long will it take to pay off $8,000 at 19.99% APR?
With $350 a month, 30 months — 2 years and 6 months. The total paid is $10,153.28 and the interest is $2,153.28. At $250 a month it takes 47 months; at $500 a month it takes 19 months.
How does the debt snowball method work?
List your debts from the smallest balance to the largest, pay the minimum on all of them, and throw every spare dollar at the smallest one until it is gone — then roll that whole payment onto the next smallest. For example: a $500 store card first, then a $2,000 credit card, then an $8,000 loan. The quick first win keeps people going.
What monthly payment clears $8,000 in 2 years?
$407.13 a month clears an $8,000 debt at 19.99% in 24 months. To clear it in 12 months takes $741.04 a month; in 36 months it takes $297.27 a month. At $350 a month, the most you can clear in 24 months is $6,877.46.
How much interest will I pay on $8,000 at 19.99%?
$2,153.28 at $350 a month over 30 months. At $250 a month the interest is $3,524.36; at $500 a month it is $1,381.87. A lower APR helps too: at 12% the interest is $1,128.36, and at 24.99% it is $2,975.11.
What if my payment does not cover the interest?
Then the debt never shrinks — the balance grows every month. At the defaults the first month’s interest is $133.27, so a payment of $133.27 or less never pays the debt off. This calculator shows a clear error in that case instead of a meaningless number: raise the payment above the monthly interest.
Why is my final payment so small?
Because the exact payoff lands just past a whole number of months. At the defaults the exact payoff is 29.01 months, so 29 full payments of $350 leave only $3.22 of balance, and one month of interest makes the final payment $3.28. A tiny final payment is normal — it means the last full payment almost finished the job.
Snowball vs avalanche: which pays less interest?
The avalanche (highest APR first) always pays less interest in total, because it attacks the most expensive debt first. The snowball (smallest balance first) wins on motivation: the first debt disappears fastest. On one debt they are identical — the difference is only the order across several debts.
Does the snowball work with a loan and cards mixed?
Yes. Order every debt by balance, whatever its type: the $500 store card, then the $2,000 credit card, then the $8,000 loan. Keep paying the minimum on the loan and the card while you attack the smallest one, then roll the freed payment forward.