There are two sensible ways to pay off multiple debts, people argue about them endlessly, and the argument is usually conducted without numbers.
Spendly runs both against your actual debts and shows you the difference.
The Two Strategies
You pay the minimum on everything, then throw every spare pound at one debt. The only question is which debt.
- Avalanche — attack the highest interest rate first. Mathematically optimal: it always costs the least total interest.
- Snowball — attack the smallest balance first. Costs more, but you clear individual debts sooner, which some people need in order to keep going.
The honest position is that avalanche wins on arithmetic and snowball wins on psychology, and which matters more depends entirely on whether you’ll still be doing this in eight months.
What Spendly Shows You
Enter each debt with its balance, APR and minimum payment, then say how much extra you can put in each month. Spendly runs a full month-by-month amortisation for both strategies and gives you:
- Debt-free date under each strategy
- Total interest paid under each
- Interest saved by choosing avalanche over snowball — the actual number, for your actual debts
- The payoff order so you know which debt is next
That last figure is the one that matters. “Avalanche is mathematically better” is not a decision. “Avalanche saves you £340 and gets you there two months sooner” is.
Sometimes the gap is trivial — if your debts have similar rates, avalanche might save you £40 over three years, and in that case you should absolutely take the snowball and the motivation that comes with it. You can only know that by running the numbers.
When the Plan Doesn’t Work
If your minimum payments don’t cover the interest, no payoff plan exists — the balance grows no matter what you do. Spendly detects this and tells you, rather than producing a fake schedule stretching decades into the future.
It’s the most useful result the tool can give you, because it means no repayment order will fix this on its own — the lever is more income, less spending, or restructuring with the lender.
Debts in Different Currencies
Debts are compared and paid down within a single currency. A euro loan and a sterling credit card are separate plans, each with its own debt-free date, because that’s the truth of it — throwing a spare pound at a euro balance means buying euros first, at whatever rate you get that day.
Spendly doesn’t blur this. Each currency gets its own honest schedule, and your net worth view converts everything into your base currency so you can still see the total picture.
For anyone paying down debt in a country they no longer live in, this distinction is the whole game.
Where the Extra Payment Comes From
The strategy is the easy part. Finding the surplus is the real work, and it usually comes from the same three places: a subscription audit, a category that’s quietly grown, and the irregular bills that keep forcing you back onto the card.
- Subscription tracking — the recurring charges you’ve stopped noticing
- Budget planning — where the money is actually going
- Sinking funds — so the next annual bill doesn’t undo six months of progress
That last one is the difference between paying debt down and paying it down permanently.