What next?
Clearing debt is one of three questions. These are the other two, and what to do with the money afterwards.
What your result means
Interest saved by avalanche is the whole financial case for choosing rate order over balance order — often a modest figure, which is worth knowing before you agonise over the choice. Time to clear is when the last debt reaches zero; the two strategies are frequently within a month of each other because the same total leaves your account either way. First debt gone is where they really differ: snowball retires a whole debt early, avalanche often leaves every balance open for much longer.
Why this one is different
Both strategies are computed here, not just discussed: you get the payoff order for each, both payoff curves on one chart, and the gap between them stated in pounds and months. The worked example below is computed by script against the live tool, so the figures on this page are proven to match what the calculator produces.
Avalanche wins the arithmetic; snowball wins the year
Both strategies pay every minimum and throw the same spare money at one target debt, so the money leaving your account is identical. The only variable is which debt receives the extra — and the difference in total interest is usually smaller than people expect.
What differs sharply is when the first debt disappears. Closing an account is the moment the plan starts feeling real, and a plan you abandon in month four costs far more than the interest the avalanche would have saved.
How it works
Both strategies pay every debt its minimum every month and put your extra payment entirely into one target debt. Snowball targets the smallest balance, avalanche the highest rate. The calculator charges one twelfth of each debt’s APR on its balance, applies the minimums, then puts everything left over into the current target. When a debt clears, its minimum plus the extra rolls onto the next target — which is what makes the payment snowball. It steps forward month by month until every balance is zero, totalling the interest as it goes.
How to use this calculator
- Choose your currency.
- Enter the extra payment you can add each month on top of the minimums. This is the only figure you control, and it matters far more than the strategy.
- Fill in each debt’s balance, rate and minimum payment — all three are on the statement. Leave unused rows at 0.
- Compare the two total interest figures to see what rate order is actually worth to you.
- Check first debt gone. If avalanche pushes that far out, snowball may be the plan you actually finish.
Formula
Each month every open debt is charged interest and paid its minimum; whatever remains of the pool goes to the first debt in the strategy’s order. The pool stays constant as debts clear, so the freed-up minimums roll onto the next target automatically.
Example calculation
Two debts — a £3,000 card at 27.9% (minimum £75) and an £800 card at 12.9% (minimum £20) — with £150 extra a month:
Avalanche targets the 27.9% card: month one it gets 75 + 150 = £225
Snowball targets the £800 card: month one it gets 20 + 150 = £170
Snowball: 20 months, interest ≈ £923.69
Avalanche: 19 months, interest ≈ £767.38
Avalanche saves £156.31 — but snowball clears a whole debt in month 5, against month 17
Frequently asked questions
Which method should I actually use?＋
Use avalanche if the interest figure above is large enough to motivate you, and snowball if it is not. The saving is real but often modest, while the risk of giving up is the expensive outcome. There is no penalty for switching: run both, pick the one you believe you will still be doing in a year.
Why do both strategies often finish in the same month?＋
Because the same total leaves your account every month in both plans. Rate order only changes how much of that money is eaten by interest rather than principal, which shifts the finish line by a month or two rather than years. The dramatic gains come from raising the extra payment, not from reordering.
Do minimum payments really stay fixed?＋
No — card minimums are typically a percentage of the balance and fall as it drops, which is exactly why they take so long to clear anything. This calculator holds them flat, matching what a real payoff plan does: you keep paying the original amount rather than letting it shrink. That is the conservative and more useful assumption.
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Assumptions & limitations
Every figure here comes from a simplified model. Keep these limits in mind when reading your result:
- Assumes fixed rates, fixed minimum payments and no new borrowing on any of the debts.
- Interest is applied monthly on the closing balance. Cards that calculate interest daily give slightly different totals.
- Minimum payments are held constant rather than falling with the balance, which is what a payoff plan does in practice.
- Excludes fees, promotional 0% windows that later revert, balance-transfer costs and any early-repayment charge on a fixed loan.
- Ignores everything outside the arithmetic: an emergency fund, employer pension matching and any debt with a lender-imposed order all take priority over optimising interest.
- If you cannot cover the minimums, this is the wrong tool — free debt advice from a charity is, and neither strategy applies until the payments are affordable.