Debt Payoff Calculator — Snowball vs Avalanche Method
Compare the debt snowball and avalanche methods to find the fastest or cheapest way to become debt-free. All calculations happen locally — nothing leaves your browser.
What is the difference between the debt snowball and the debt avalanche? Both methods pay the minimum on every debt and put one fixed extra payment on a single target account. The snowball targets the smallest balance first; the avalanche targets the highest interest rate first. Because interest builds fastest on the most expensive balance, the avalanche normally costs less overall — on the three sample debts loaded here it saves roughly $600 and finishes four months sooner.
How to Use the Debt Payoff Calculator
- Add each debt you owe — Enter a name, the current balance, the interest rate and the minimum monthly payment, then press Add Debt. Three sample debts are loaded to show the output; remove them with the red × once your own are in.
- Enter the annual rate, not the monthly one — The simulation divides whatever you type by 12 to get a monthly rate, so enter the APR from your statement. A card quoted at 20% APR becomes 1.667% per month here.
- Copy the minimum payments from your statements — The minimum is what keeps the account current, and it drives the whole schedule. If a minimum is smaller than one month's interest the balance grows instead of shrinking, and the payoff date runs away.
- Set one extra monthly payment — This is the amount above all the minimums that you can commit every month. It is held constant for the entire simulation and is applied to whichever debt the chosen method targets, spilling over to the next debt once one is cleared.
- Compare the two method cards — Each card shows months to payoff and total interest. The green border marks the method with the lower total interest, and a tie is awarded to the snowball. The chart plots both remaining-balance curves so you can see where they separate.
- Read the month-by-month schedule — The table underneath follows the avalanche order and lists payment, interest, principal and remaining balance for each month, up to 120 rows. It is also the source of the four headline stat cards.
How the Payoff Simulation Works
The calculator does not use a closed-form formula. It steps forward one month at a time and repeats the same four operations until every balance reaches zero, which is the only way to model several debts with different rates competing for one pot of money.
Monthly interest = balance × (annual rate ÷ 100 ÷ 12)- Charge interest. Each open debt accrues one month of interest at its own rate and that amount is added to the balance. This is simple monthly accrual from the nominal APR, the convention most card and loan statements use.
- Pay the minimums. Every open debt receives its minimum payment, capped at the remaining balance so the last month never overpays.
- Rank the debts. The snowball run sorts by current balance, smallest first. The avalanche run sorts by interest rate, highest first. This is the only line that differs between the two strategies.
- Apply the extra. The extra payment goes to the debt at the top of that ranking. If it is more than the balance, the remainder cascades to the next debt in line, so no money is wasted in the month an account clears.
Because the snowball ranks by current balance rather than starting balance, a large debt that has been paid down can move to the front of the queue partway through — which is how the method behaves in practice too.
One thing the model holds constant
The extra payment is exactly the figure you typed, every month, for the whole run. When a debt is cleared its minimum simply stops being paid; that freed money is not automatically rolled into the next debt. A textbook snowball does roll it forward, and that rollover is where the method gets its name. To model it here, raise the Extra Payment field by the minimum of each debt as it clears and re-run. Treat the figures on this page as a conservative floor: a real rollover plan finishes sooner and costs less interest than what you see.
Two other boundaries are worth knowing. The simulation gives up after 600 months, so a scenario whose minimums never outpace the interest reports 600 rather than looping forever. The schedule table stops at 120 rows even when the payoff runs longer than ten years, though the stat cards above it still show the full figure.
Snowball or Avalanche
The two methods differ in one decision — which debt gets the extra money — and that decision trades money against momentum.
| Debt Snowball | Debt Avalanche | |
|---|---|---|
| Target | Smallest remaining balance | Highest interest rate |
| Optimises for | Number of accounts closed early | Total interest paid |
| First win arrives | Sooner — small accounts clear quickly | Later — the expensive debt is often a large one |
| Costs more interest | Usually yes | Usually no |
| Best when | You have stalled before and need visible progress, or several small balances are cluttering your accounts | Rates vary widely across your debts, so the gap between them is worth real money |
| Sample result here | 43 months, about $3,100 interest | 39 months, about $2,500 interest |
When every debt carries a similar rate the two orders produce almost the same result, and you should simply pick the one you will actually follow. The gap widens as the rates spread apart: a 24% store card sitting next to a 4% car loan is where the avalanche earns its keep.
What an Extra Payment Actually Buys
The single largest lever is not the ordering but the size of the extra payment. The table below runs the three preloaded sample debts — a $5,000 card at 20%, a $12,000 car loan at 5.5% and a $3,000 personal loan at 10%, with $500 of combined minimums — at different extra amounts.
| Extra per month | Snowball | Avalanche | Interest saved by avalanche |
|---|---|---|---|
| $0 | 109 months, ~$7,700 | 109 months, ~$7,700 | $0 |
| $100 | 52 months, ~$4,100 | 48 months, ~$3,300 | ~$780 |
| $200 | 43 months, ~$3,100 | 39 months, ~$2,500 | ~$620 |
| $300 | 36 months, ~$2,500 | 33 months, ~$2,100 | ~$450 |
| $500 | 27 months, ~$1,800 | 26 months, ~$1,600 | ~$280 |
Three things stand out. With no extra payment at all the two methods are identical, because there is nothing to allocate and the ordering question never arises. The first $100 is worth far more than the fifth: it cuts more than four years off the timeline, while going from $300 to $500 saves under a year. And the advantage of the avalanche shrinks as the extra payment grows — once you are clearing debt quickly, the order matters less because nothing sits accruing interest for long.
That last point is the practical takeaway. If choosing the snowball is what gets you to commit $200 a month instead of $100, the snowball is the better plan for you, and the interest arithmetic will not disagree by enough to matter.
Where the Model Stops Matching Reality
Every debt here carries one fixed rate for the whole term. Real accounts do not always behave that way. A promotional 0% balance transfer reverts to a much higher rate on a known date, and modelling it as a single blended rate will make the payoff look easier than it is. Variable-rate cards move with the base rate. Annual fees, late fees and payment protection premiums are not modelled at all, so add them into the balance or the minimum if they are material.
The minimum payment is also treated as a fixed dollar amount. Most credit cards set the minimum as a percentage of the balance, typically with a floor, so the real minimum falls as you pay down and the account takes longer to clear on minimums alone than a constant figure suggests. If you want the pessimistic view, enter the minimum your statement shows today and check it again in six months.
Finally, this is an interest calculation, not a financial plan. It has no view on whether you should keep an emergency fund before overpaying, whether an employer retirement match beats a 6% loan, whether a balance transfer or consolidation loan would reset the whole picture, or whether a debt is close enough to statute or to a hardship arrangement to be handled differently.
This calculator is an informational tool, not financial advice. It works only from the balances, rates and payments you type in and ignores fees, promotional rates and changes in your circumstances. For decisions about consolidation, refinancing or hardship arrangements, speak to a qualified financial adviser or a non-profit credit counselling service.
Frequently Asked Questions
Both pay the minimum on every account and direct one fixed extra payment at a single target. The snowball targets the smallest remaining balance, so accounts close quickly and progress is visible. The avalanche targets the highest interest rate, so the most expensive balance stops growing first. Only the ordering differs — the money you commit each month is identical, and so is the total you owe at the start.
Run both with your own numbers and look at the size of the gap. If the avalanche saves a few hundred dollars over three years, that is real money but it will not rescue a plan you abandon in month four. If it saves several thousand — which happens when one debt sits far above the others on rate — the arithmetic deserves more weight. Consistency beats optimality: the best method is the one you keep doing.
No. The extra payment stays at exactly the figure you enter for the whole simulation, and when a debt clears its minimum simply stops. A textbook snowball rolls that freed minimum forward, which is where the name comes from. To model it, increase the Extra Payment field by each minimum as that debt is paid off and re-run. The months and interest shown here are therefore a conservative estimate — a genuine rollover plan finishes sooner.
As much as you can hold to without draining the buffer that stops you reaching for the card again. The returns are front-loaded: on the sample debts, the first $100 a month cuts the payoff from 109 months to 48 and saves over $4,000 of interest, while raising the extra from $300 to $500 saves under a year. Try three figures in the Extra Payment field and pick the largest one you can commit to every single month.
Include anything you genuinely intend to overpay. In practice mortgages sit at much lower rates over much longer terms, so they land at the bottom of an avalanche queue and mostly just make the chart harder to read. Government student loans often carry repayment terms, forgiveness rules or income-linked caps that this simple model cannot represent, so check those separately before diverting money to them.
The simulation runs entirely in JavaScript in your browser and no balance, rate or payment is uploaded or stored on a server. One caveat worth taking seriously: your full debt list and extra payment are also written into the page URL so a scenario can be bookmarked or reloaded. That link contains every balance you entered, so do not paste it into a chat, a ticket or a shared document.
Because a minimum payment is smaller than one month's interest on that debt, so the balance grows faster than it is being paid down. The simulation stops after 600 months rather than looping forever. Check the rate you entered is an annual APR rather than a monthly figure, then check the minimum against the interest: a $5,000 balance at 20% accrues about $83 a month, so anything below that never touches the principal.
The headline stats — total interest, months to payoff and total paid — are all taken from the avalanche run, as is the month-by-month schedule at the bottom of the tool. The two comparison cards in the middle are the only place the snowball figures appear. If you have decided on the snowball, read the blue card for your timeline and treat the schedule table as an approximation of the order rather than of the dates.
No. Each debt carries one fixed rate for the whole term, one fixed minimum in dollars, and no fees. Real credit cards usually set the minimum as a percentage of the balance, so it falls as you pay down, and a 0% balance transfer reverts on a set date to a much higher rate. Annual fees and late charges are not modelled either. Where these matter, add them into the balance or the minimum before you compare methods.
Use Cases
Settling a Snowball-or-Avalanche Argument
Two people in a household disagree about which card to attack first. Enter the real balances and rates, run both, and let the size of the gap decide it instead of the strength of the opinion.
Deciding What to Do With a Raise
Run the current extra payment, then run it again with the after-tax increase added. The difference in months and interest tells you what redirecting the raise is worth before it quietly gets absorbed into everyday spending.
Sanity-Checking a Consolidation Offer
Model your current debts as they stand, then model the consolidation loan as a single debt at its quoted rate and term. Compare total interest on both. A lower monthly payment over a longer term often costs more overall.
Setting a Realistic Debt-Free Date
Turn a vague intention into a month on the calendar. Adjust the extra payment until the timeline lands somewhere you believe in, then work backwards to what has to change in the monthly budget to fund it.
Seeing the Cost of Minimums Alone
Set the extra payment to zero and read the months and total interest. For most credit-card balances the result is startling enough to be the argument for finding an extra payment in the first place.
Preparing for a Credit Counselling Appointment
Arrive with every balance, rate and minimum already listed in one place and a printed schedule of where the money goes. The session can then be spent on options rather than on assembling the picture from statements.