Debt-Free Date
Nov 2029
39 months
£25,500.00
£2,673.03
£2,737.31
54 months faster
A payoff date is only real if the extra payment survives the month
iBudget tracks your spending against a budget so the money for your avalanche payment is still there on payday.
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- 1
Credit Card
19.99% APR • Month 10
Jun 2027
- 2
Car Loan
6.5% APR • Month 22
Jun 2028
- 3
Student Loan
5.5% APR • Month 39
Nov 2029
Monthly Payment: £725.00(£525.00 minimums + £200.00 extra)
Minimum Only
- Time:
- 93 mo
- Interest:
- £5,410.34
Snowball
- Time:
- 39 mo
- Interest:
- £2,673.03
Avalanche
Best- Time:
- 39 mo
- Interest:
- £2,673.03
How this calculator works
Not an amortisation formula. A month-by-month simulation of where every pound or dollar of your payment goes.
The formula
each month: b ← b + b × (APR ÷ 100 ÷ 12); b ← b − min(m, b); pool = extra + Σ unused m; pool → highest APR first- b
- The remaining balance on one debt, carried from month to month. Interest is added before any payment is taken off.
- APR
- That debt's annual rate exactly as you typed it. The code computes rate / 100 / 12 — a nominal monthly rate, not a compounded twelfth root, and applied monthly rather than daily.
- m
- The contractual minimum payment for that debt. Held constant for the whole projection, even though real card minimums fall as the balance falls.
- pool
- This month's redirectable money: your extra payment, plus the minimums of debts already cleared, plus any part of a minimum this month's debt did not need.
- order
- Debts sorted by rate, highest first. The sort is stable, so equal rates keep the order you entered them in.
- stop
- The loop ends when every balance is zero, at 600 months, or the moment a month closes with the total balance no lower than it opened.
Totals are rounded to two decimals only at the end; the simulation itself runs in full floating point, and any balance under half a cent is treated as cleared. The snowball and minimums-only columns run the same engine with two changes: the snowball sorts by smallest balance instead of highest rate, and the minimums-only run adds no extra payment and never redirects a freed minimum.
The avalanche is not really a formula, it is a monthly loop, and the calculator on this page runs that loop up to 600 times. Every month it does the same four things in the same order: it accrues interest on each outstanding debt, it pays each debt its contractual minimum, it gathers up every pound or dollar that is now spare, and it throws that pool at whichever debt has the highest interest rate. Nothing is estimated with an amortisation shortcut — the balances are simulated month by month, which is why the tool can tell you the exact month each individual debt disappears.
The part most calculators get wrong is the spare pool. It is not just your extra payment. It also contains the minimum payments of debts you have already cleared, which you are no longer sending anywhere, and it contains any unused part of a minimum this month — if a debt needs $38 to close and its minimum is $105, the other $67 rolls straight onto the next debt rather than vanishing. The invariant the engine holds to is that the total money leaving your account in any month is exactly the sum of all your minimums plus your extra payment. Never more. That is what stops a payoff projection quietly spending money you do not have.
Interest is applied before payment, on the whole outstanding balance, at APR divided by twelve. That is a nominal monthly conversion rather than a true compounded one, and it is applied once a month rather than daily. It is the standard convention for payoff projections and it is close enough for planning, but it is a simplification and you should expect your real statements to drift from it by small amounts.
The minimums-only column is deliberately built differently. It runs the same interest and minimum-payment steps but never redirects a freed minimum and never adds an extra payment, because that is what actually happens when someone pays the minimum and spends the difference. That is why the gap between the two columns is usually so large: the avalanche column recycles money the minimums-only column throws away.
The three moves, in order
- 1
Sort by rate, not by size
List every debt from highest APR to lowest. Balance is irrelevant to the ordering.
- 2
Minimums everywhere, extra in one place
Protect every account with its minimum, then send every spare pound or dollar to position one.
- 3
Roll the freed payment forward
When a debt clears, its minimum joins the extra payment and the whole amount attacks the next-highest rate.
A worked example
One US household, four debts, one extra payment of $250 a month. Figures produced by the calculator on this page.
$24,100 across four debts, $250 extra a month
Worked example- Store card — 28.9% APR, minimum $105
- $4,200
- Visa — 22.9% APR, minimum $150
- $6,000
- Personal loan — 9.9% APR, minimum $80
- $2,400
- Car loan — 7.4% APR, minimum $310
- $11,500
- Total minimums + extra, every month
- $645 + $250 = $895
- Month 1 interest across all four debts
- $306.37
- Month 1 extra payment, all to the store card
- $250
- Total balance after month 1
- $23,511.37
Month 1 in full: interest accrues at $19.80 on the personal loan, $101.15 on the store card, $114.50 on the Visa and $70.92 on the car loan, taking the balance to $24,406.37. The four minimums remove $645. The $250 extra goes entirely to the 28.9% store card because it holds the highest rate, even though the personal loan has the smallest balance. Net reduction: $588.63, which is the $895 paid less the $306.37 charged. Run the same debts through the snowball and you get 34 months and $5,511.42 of interest — the avalanche saves $644.59 and one month. Run them on minimum payments only and you get 139 months and $17,789.04 of interest. The avalanche saves $12,922 against that, which is the comparison worth caring about.
How to read your result
What a good number looks like, what a bad one means, and what to do about each.
Three numbers come out of this calculator and they answer different questions. The debt-free date tells you whether the plan is survivable — 33 months of discipline is a real ask, 90 months is a different life. The total interest tells you what the debt is costing you to keep. And the saving versus minimum payments tells you what the plan is worth, which is almost always a far bigger number than the saving versus the snowball.
Start with your highest rate. If your top debt is above roughly 20% you are in credit card territory, and the avalanche's advantage is at its largest, because the rate gap between that debt and the rest of your queue is wide. The average US card charging interest sat at 22.15% in the second quarter of 2026 and the representative UK card rate was 24.71% in July 2026 — if your worst rate is meaningfully above those, it is worth checking whether a balance transfer or a consolidation loan could cut it before you start.
Then look at the spread. If every debt in your list is between 6% and 9%, run the numbers and you will find the avalanche and the snowball land within a rounding error of each other, and the ordering question genuinely does not matter — pick whichever you will keep doing. If you have a 29% store card sitting alongside a 7% car loan, the ordering matters a great deal and the avalanche is unambiguously the better plan.
Finally, check the monthly total the calculator shows at the foot of the schedule: all your minimums plus your extra. That figure has to survive contact with a real month. A payoff date built on an extra payment you cannot actually make every month is not a plan, it is a wish, and it is the single most common reason these projections fall apart.
Rates and balances to compare yourself against
US and UK figures are given side by side because the two markets price debt very differently. All are averages across large populations, so treat them as orientation rather than a target.
22.15%
Average US credit card rate on accounts charged interest
2026 Q2, preliminary. Covers only accounts that carried a balance; the all-accounts average, which includes people who pay in full, was 20.94%.
24.71%
Representative UK credit card rate
July 2026. A quoted rate on advertised card lending, remarkably flat since 2025, and it excludes 0% promotional balances.
Source: Bank of England, quoted household interest rates (IUMCCTL)
25.2% / 31.3%
Average US APR on general purpose cards vs store cards
2024, the highest since at least 2015. These are stated APRs across accounts, which is why they sit above the Fed's 22.15% figure for rates actually assessed — the two measure different things. That 6-point gap is exactly the kind of spread the avalanche ordering exists to exploit.
6.85%
Average advertised rate on a £10,000 UK personal loan
July 2026. Quoted, not effective. A card at 24.71% and a loan at 6.85% in the same list is why order changes the answer.
Source: Bank of England, quoted household interest rates (IUMHPTL)
15%
US general purpose cardholders paying only the minimum
2024, the highest share since at least 2015; 20% on store cards. This is the group the minimums-only column is describing.
$5,300
Average monthly card balance per US cardholder
2024. An average across all cardholders including those who pay in full, so revolvers hold considerably more; it rose to about $8,700 for prime scores.
What this calculator does not account for
Every payoff projection is a simplification. These are the specific ones this tool makes.
- No fees of any kind
- Annual fees, late fees, over-limit fees, cash advance fees and balance transfer fees are all ignored. US consumers paid $31.3 billion in card fees in 2024 according to the CFPB, so this is not a rounding error for everyone. Interest is the only cost modelled.
- Every rate is fixed forever
- The APR you type is applied unchanged for the entire projection. There is no promotional 0% expiry, no variable rate tracking a base rate, and no penalty APR after a missed payment. If your plan depends on a teaser rate, model both the promo rate and the go-to rate.
- Your minimum payment never changes
- Real card minimums are a percentage of the balance and shrink as you pay down, which is what makes minimum-only repayment so slow. Holding the minimum constant makes the minimums-only comparison on this page optimistic — the true cost of paying minimums is worse than the figure shown.
- Monthly interest, not daily
- Interest is charged once a month at APR divided by twelve, on the full balance, before any payment lands. Cards compound daily on an average daily balance and most loans accrue daily. Expect small monthly differences against your real statements, and expect the calculator to charge a little interest in the month a debt clears.
- No new spending
- The projection assumes no further purchases on any card in the list, and no new debt taken on. If the card that funds your grocery shortfall is also in the plan, the plan will not happen.
- Secured and unsecured debt are treated identically
- The queue is sorted purely by interest rate. It has no idea that skipping a car payment repossesses the car, or that an arrears balance can escalate to court action. Judgement about which debts are dangerous rather than merely expensive stays with you.
- No inflation, tax or opportunity cost
- Nothing is adjusted for inflation, no tax relief is applied (US student loan or mortgage interest deductions, for instance), and the tool never asks whether the extra payment would do more in a pension, a workplace match, or a savings account. It answers one question: what does this debt cost if I pay it this way.
- Consolidation, transfers and formal debt solutions are out of scope
- Balance transfers, debt consolidation loans, debt management plans, IVAs, hardship programs and negotiated settlements can all beat every column on this page. If your result says the debt never clears, those are the routes worth exploring, not a bigger extra payment you cannot afford.
- Rounding and limits
- The simulation runs in full floating point and rounds only the final interest and total-paid figures to two decimals. Balances under half a cent are treated as cleared. The loop stops at 600 months, or earlier if a month ends with the total balance no lower than it started, in which case the result reports that the plan never clears.
None of this makes the projection useless. It makes it a planning estimate rather than a statement of account, and the direction of most of the errors is knowable: fees and daily compounding make the real cost slightly higher, and a declining minimum payment makes the minimums-only column much worse than shown.
Debt avalanche questions, answered
Including the ones where the answer is not the one the method would like.
What is the debt avalanche method?
You pay the contractual minimum on every debt you owe, then send every spare pound or dollar to whichever debt carries the highest interest rate — regardless of how big or small that balance is. When it clears, its minimum payment joins the spare money and the whole amount moves to the next-highest rate. Because interest is charged as a percentage of what you owe, killing the most expensive percentage first means the least interest is ever charged.
How is the avalanche different from the snowball method?
Only the sort order changes. The avalanche sorts your debts by interest rate, highest first; the snowball sorts them by balance, smallest first. Every other mechanic is identical — same minimums, same extra payment, same rolling-up of freed payments. The avalanche always costs less in interest or ties; the snowball almost always clears your first individual debt sooner.
How much does the avalanche actually save me?
Usually less than you would hope, and the honest answer is that it depends entirely on the gap between your rates. In the worked example on this page — four debts totalling $24,100 — the avalanche saves $644.59 and finishes one month earlier than the snowball. Against paying minimums only it saves $12,922, which is the comparison that really matters. If your rates are all within a few points of each other, the two methods produce nearly identical results and you should simply pick the one you will stick to.
Does the calculator charge interest daily or monthly?
Monthly. Each month it adds balance x (APR / 100 / 12) to every outstanding debt before any payment is applied. Real credit cards compound daily on the average daily balance, and most loans accrue daily too, so your real statement will differ from this projection by a small amount each month. Over a two- or three-year plan that difference is typically tens of dollars, not hundreds.
Why does my result say the debt is never cleared?
That appears when your minimum payments plus your extra payment are not enough to outrun the interest. The engine checks the total balance at the end of each month against the total at the start; if the balance has not fallen, it stops and reports that the plan never clears. It also gives up after 600 months. If you see this, the answer is not a longer timeline — it is a higher payment, a lower rate, or free debt advice.
Should I include my mortgage and car loan?
Include anything you want the plan to pay off, but be careful about what the ordering implies. The calculator treats every debt as interchangeable, so a 7% auto loan and a 7% credit card sit in the same place in the queue. In real life missing a car payment loses you the car and missing a mortgage payment loses you the house, so those minimums are not optional in the way a card minimum is. Most people run this on unsecured debt only — cards, store cards, overdrafts, personal loans, buy-now-pay-later — and leave the mortgage out entirely.
What happens if two debts have the same interest rate?
The sort is stable, so tied debts stay in the order you entered them and the extra payment goes to whichever you listed first. If you care which one clears first — and you might, if one is with a lender you want rid of — reorder your rows or nudge one rate by 0.01 to break the tie deliberately.
Can I model a 0% balance transfer card?
You can enter 0 as the rate and the calculator will accrue no interest on it, which is correct for the promotional period. What it cannot do is switch that rate back to 24.9% on the month the promotion ends, because it holds every rate fixed for the entire projection. If you are relying on a 0% deal, run the calculator twice — once at 0% and once at the go-to rate — and treat the honest answer as somewhere between the two, weighted by how confident you are of clearing it in time.
My credit card minimum changes every month. What do I enter?
Enter this month's minimum. Card minimums are usually a percentage of the balance plus interest and fees, so they fall as the balance falls, whereas this calculator holds the figure you type constant for the whole projection. That makes the avalanche and snowball columns slightly conservative and the minimums-only column considerably optimistic — a real declining minimum takes far longer to clear a card than a fixed one. The Money Charity models a UK card on the average rate taking 27 years and 10 months on true legal minimums.
Should I build an emergency fund before starting the avalanche?
Most debt advisers say keep a small buffer — a few hundred, or one month of essential bills — before throwing everything at the balances, because otherwise the next broken boiler goes straight back on the card you just cleared. Bankrate's 2026 survey found 29% of Americans have more credit card debt than emergency savings. A buffer that stops you re-borrowing at 22% is worth more than the interest it forgoes.
Is the avalanche ever the wrong choice?
Yes, in two situations. If the interest saving is small and you have failed at debt payoff before, the snowball's early wins are worth more than a few hundred in interest, because a plan you abandon in month four saves nothing at all. And if one debt has consequences that are not financial — a family loan, an arrears balance that could lead to court action, a car you need for work — clear that first regardless of its rate.
Will paying debt off this way hurt my credit score?
Cutting revolving balances usually helps, because credit utilisation is one of the largest scoring factors and the avalanche targets high-rate revolving debt first. Closing accounts as you clear them can nudge your score down by reducing your total available credit, so consider leaving cleared cards open and unused. Note that scoring models differ by country and by bureau, and this calculator does not model scores at all.
Read next
Read next
- Debt snowball vs avalanche: which one should you actually use?The full comparison, including when the psychology beats the arithmetic.
- Dealing with debt: a practical UK guidePriority debts, free advice, and what to do if no payment plan adds up.
- Types of credit card explainedBalance transfer, money transfer and purchase cards, and where each one helps.
- How much emergency fund do I actually need?The buffer that stops the debt you just cleared coming straight back.
- The 50/30/20 ruleWhere the extra payment comes from in the first place.
Other calculators
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