What this planner works out
This planner takes your monthly income and five categories of spending, and returns three figures: total spending, what is left over, and the percentage of income you are spending. The arithmetic is exact — it adds up what you enter and subtracts it from income.
The difficulty is never the sum. It is that most people underestimate their own spending by a wide margin, because irregular costs do not appear on any single month's bank statement. The guidance below is aimed squarely at that problem.
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Before you fill this in
- Work from bank and card statements rather than memory. Three months is enough to expose most of the pattern; twelve is better if you can face it.
- Use take-home pay, not gross salary. If your income varies, use the lowest of the last three months rather than an average — a budget that only works in a good month is not a budget.
- Divide annual and quarterly costs by twelve and include them. Car insurance, MOT, servicing, TV licence, subscriptions billed yearly and Christmas all belong in a monthly figure.
- Put anything you cannot classify into other spending rather than leaving it out. An honest large number is more useful than a tidy small one.
Fixed costs are the same every month, such as rent. Variable costs change with behaviour, such as food and fuel. Irregular costs arrive occasionally but predictably, such as an annual renewal. Budgets usually fail on the third category, because it is the one that never appears on the statement you happen to be looking at.
How this calculator works
The planner performs two calculations and one ratio:
Total spending = housing + bills + food + transport + other
Left over = income − total spending
Proportion spent = total spending ÷ income × 100The left-over figure is what remains for saving, debt repayment and anything not already listed. If it is negative, spending exceeds income and the shortfall is being covered by savings, credit or an overdraft.
The percentage matters more than the pound figure when comparing one month with another, or when your income changes. Spending 85% of income is the same pressure whether that is £2,000 or £6,000.
Worked example: £2,500 a month
Using the default figures — income £2,500, housing £900, bills £400, food £350, transport £180 and other spending £300:
- Total spending: £900 + £400 + £350 + £180 + £300 = £2,130
- Left over: £2,500 − £2,130 = £370
- Proportion spent: £2,130 ÷ £2,500 = 85.2% of income
£370 a month sounds comfortable until you remember what is not in the list. If car insurance, a service, a birthday and a boiler repair all land in the same quarter, that £370 disappears and the month goes into overdraft. This is why the irregular costs need dividing by twelve and adding in — once they are included, the honest left-over figure is often half what people expect.
Common budgeting mistakes
- Budgeting from memory. Recalled spending is consistently lower than actual spending, particularly on food and small card payments.
- Leaving out irregular costs. The single most common reason a budget that balances on paper fails in practice.
- Using gross pay. Income tax, National Insurance, pension contributions and student loan repayments come out first.
- Treating the left-over figure as spending money. It is the total available for saving, debt repayment and everything that has not been listed.
- Building a budget so tight it cannot survive a bad week. A plan with no slack is abandoned at the first unexpected cost.
Frequently asked questions
What proportion of income should go on housing?
A frequently quoted guideline is around a third of take-home pay, but it is a rule of thumb rather than a rule. What matters is whether the remainder covers everything else with something left over. In parts of the UK, a third is unattainable; in others, it would be generous.
My income changes every month. How should I use this?
Budget against the lowest month you can reasonably expect, and treat anything above that as surplus to be allocated deliberately — to a buffer first, then to savings or debt. Budgeting against an average means roughly half your months are planned to fail.
Should pension contributions count as spending or saving?
If they are deducted before you are paid, they are neither — they never reach your take-home pay, so simply use the net figure. If you pay into a pension from your bank account, treat it as saving rather than spending, and record it separately from the five categories here.
What should I do if the left-over figure is negative?
Deal with it as a priority rather than a background worry. Look first at whether it is genuinely structural or the result of a one-off month. If it is structural, free debt advice is available in the UK from Citizens Advice, StepChange and National Debtline, all of which are free and confidential. MoneyHelper can point you to the right one.
Is my budget stored anywhere?
No. Every figure is processed in your browser and nothing is transmitted or saved. Closing the tab discards it, so write down or screenshot anything you want to keep.
Related tools
References
- MoneyHelper — free and impartial UK money guidance, including budgeting and debt support
- GOV.UK — current tax, National Insurance and benefit rates affecting take-home pay
Sources are checked at publication and can change — how I choose and check references.