Track your income and expenses, convert every cost to a monthly figure, and see exactly how much spare cash you have to throw at your debt each month.
5 min readUpdated: 25 Jul 2026UK
A budget planner tracks your income and outgoings so you can see how much spare cash is left each month. With the average UK household spending over £2,500 a month, the surplus you free up is what powers your debt snowball. This planner converts weekly and annual costs to monthly and shows your leftover figure instantly.
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The debt snowball and avalanche both run on one number: your monthly surplus. That's the money left over after every essential is paid. This planner works it out for you by converting every income source and expense — however often it's paid — into a single monthly figure, then subtracting outgoings from income.
Once you can see that number clearly, two things happen. First, you know exactly how much extra you can commit to your debt payoff plan. Second, the category breakdown shows where your money actually goes, so you can find more surplus by trimming the categories that have quietly crept up.
Little costs add up
The planner flags smaller recurring payments (under £50 a month) separately, because these are the costs people most often overlook. A daily coffee, a handful of streaming subscriptions, and a couple of takeaways can easily total £150–£200 a month — enough, redirected, to shave years off a credit-card balance.
Add every income source and expense, choosing a category and how often it's paid. The planner converts everything to a monthly figure, then shows total income, expenses, net balance, a category breakdown, and charts. The net balance is the spare cash you could put toward debt or savings.
Weekly costs are multiplied by 52.18 then divided by 12 (about 4.35 weeks per month). Bi-weekly uses 26.09 payments a year. Quarterly is divided by 3, annual by 12 — giving an accurate average monthly figure.
A popular starting point is 50/30/20: 50% of take-home pay on needs, 30% on wants, 20% on savings and debt. If you're clearing debt, many people prioritise debt payments. The key idea is that every pound has a job.
Budgeting reveals your net monthly surplus — the money left after essentials. That surplus powers the debt snowball or avalanche. Even finding an extra £100–£200 a month by trimming small recurring costs can cut years off a repayment plan.
There is no single rule, but a common target is to put at least 20% of your take-home pay toward debt and savings combined, weighted toward debt while balances carry high interest. The right figure is whatever surplus your budget can sustain without missing essentials. Use this planner to find that surplus, then send as much of it as you safely can to your payoff plan.
Build a small starter emergency fund first — around £1,000 or one month of essentials — then focus on clearing high-interest debt. Without any buffer, an unexpected bill pushes you straight back onto the credit cards and undoes your progress. Once expensive debt is gone, grow the fund to three to six months of expenses.
Disclaimer: This tool is for informational purposes only and does not constitute financial advice. Figures are estimates based on the information you enter. For personal advice, consult an FCA-regulated adviser. If your budget shows a shortfall and you are struggling to cover essentials, free debt advice is available — contact StepChange (0800 138 1111) or National Debtline (0808 808 4000). You never have to pay for debt advice.
How this calculator works›
The method
The planner totals your income and your spending, converting everything to a monthly figure first so items paid at different frequencies compare like for like — weekly amounts are multiplied by fifty-two and divided by twelve, and annual amounts are divided by twelve. Your monthly surplus is simply total monthly income minus total monthly spending: the spare cash you can redirect to debt payoff or savings each month.
Assumptions & limitations
Figures are only as accurate as the amounts you enter; average irregular or seasonal costs across the year for a realistic picture.
It is a snapshot of your current monthly position — it does not forecast tax, benefits or future price changes.
The surplus shown is before any extra debt payment; how you deploy it is up to you.
Data sources
Every calculation runs in your browser on the balances and rates you enter, so the
results reflect your own figures.
The approach follows standard UK personal-finance conventions; for reference figures and guidance we point to MoneyHelper and the Bank of England.
Figures and rules change over time — always check the original source.
Written and reviewed by Peter Barclay,
a UK Chartered Mechanical Engineer — who builds and maintains these tools, pairing
engineering-mathematics training with a focus on the mechanics of debt repayment. The calculators use standard amortization formulas and fixed
repayment orders. Read our methodology
or more about the author.
DebtSnowball is not a financial adviser and is not authorised or regulated by
the FCA (Financial Conduct Authority).
These tools are for education and information only, not financial advice.
If you are struggling with debt, get free, impartial help from
StepChange,
National Debtline
or Citizens Advice.
Last reviewed: July 2026·Spotted an error?
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DebtSnowball.co.uk provides free educational information and calculators, not regulated financial advice. Calculator results are estimates for illustrative purposes only, based on the figures you enter, and should not be treated as financial advice. For advice tailored to your situation, speak to a free debt-advice charity above or an adviser regulated by the FCA. This site is supported by advertising; ads do not influence our editorial content.