Work out monthly surplus or deficit from income and core expenses

Why most budgets fail

Most budgets fail not from lack of planning but from the mistake of setting them against ideals rather than actuals. A budget based on what you think you might spend rarely survives contact with what you actually spend. The single most effective change to budgeting practice is tracking real spending for one full month before committing to any budget figures. Real patterns are always different from estimates. This calculator helps you structure a budget; the commentary below is about how to make it actually stick.

The two budget frameworks that work

Category-based budgeting allocates a specific amount to each spending area (rent 800, food 300, transport 200, etc.). Simple, common, teaches discipline about category-level overspending. Works best for people who can stick to predetermined limits.

Pay-yourself-first budgeting inverts the structure: take savings and investments off the top, then spend what remains without further categorisation. Requires less tracking, handles irregular spending automatically, works best for people who struggle with category micromanagement. The savings rate is the hard constraint; the rest is flexible.

Most people start with category-based and either stick with it or drift toward pay-yourself-first as they mature financially. Both work; both can fail. The failure mode of category-based is overengineered categories that don't reflect actual spending. The failure mode of pay-yourself-first is savings rate set too low because the discipline of categorical limits isn't there.

The percentages that work for most

Budget guidance tends to cluster around these percentages (after tax):

Housing (rent/mortgage/local property tax/utilities): 30-40% of take-home. Over 40% signals over-housed relative to income.

Food (groceries + eating out): 10-15%.

Transport (car, fuel, public transport): 10-15%.

Personal (clothes, gym, subscriptions, hobbies): 5-10%.

Savings and investment: 15-25%. Below 10% signals a plan that won't build wealth at typical rates.

Buffer for irregular expenses: 5-10%. The annual-expenses that arrive monthly in disguise.

These are guidelines, not rules. Young professionals often spend 50%+ on housing; retired homeowners spend 15%. Adapt to your specific circumstances, but be honest about whether your structure is sustainable.

The hidden monthly costs

A realistic budget includes costs that don't appear every month but need monthly reservation:

Annual expenses /12: car insurance, road tax, TV licence, Christmas, birthdays, one specific annual holiday. Total typically 100-300/month.

Replacement funds: car needs replacing eventually (budget 100-300/month depending on car type), appliances break (50-100/month), furniture wears out (20-50/month).

Health and emergency: dental, opticians, pet emergencies, small medical. 50-150/month typical.

These add 200-550/month to the honest expense picture. Budgets without them produce shortfalls whenever anything irregular happens, which is continuously.

The subscription audit most people avoid

households average 8-15 active subscriptions (streaming, gym, software, magazines, meal kits, apps, cloud storage). Total monthly cost often 150-300. The ones you actually use? Usually 40-60% of what you pay. Running a subscription audit once a year and cancelling everything unused typically saves 50-150/month — more than most people's entire category-budget adjustments accomplish. This is the easiest win in most household budgets: you're already paying; you just need to stop paying for the ones that aren't earning their keep.

Why eating out destroys food budgets

Food budget splits typically go 60-70% groceries, 30-40% eating out. Food cost per calorie at restaurants is 3-5× the cost at home. Takeaway sits between. A household eating out twice a week typically spends more on that than on all groceries combined. This isn't an argument against ever eating out — it's an argument for knowing the number. Most overspending on food happens through eating out being invisible (small individual transactions that don't feel significant). Category-tracking eating out separately from groceries usually reveals spending 30-50% higher than people believed.

The "income increased, savings didn't" pattern

The most damaging budgeting failure isn't overspending — it's lifestyle inflation matching income growth. A pay rise goes to a slightly better house, a slightly better car, slightly nicer holidays. Savings rate stays flat at whatever it was before the raise. Ten years of this produces no improvement in financial position despite cumulative 30-50% income growth. The fix: every pay rise should trigger an automatic increase to savings contributions proportional to the rise. If savings rate was 15% before the rise, it should be 15% after — which means the additional savings amount automatically comes out first.

Tracking vs budgeting

These are different. Tracking records what you spent retroactively. Budgeting sets intentions forward. Most people benefit from doing both: track for 3 months first to establish real patterns, then set budget targets based on actuals rather than ideals. Pure tracking without budgeting tends to produce awareness without discipline; pure budgeting without tracking tends to produce plans that don't match reality. Combined, they produce achievable targets.

When to revisit the budget

Useful triggers: annually at the start of the tax year, whenever income changes meaningfully (pay rise, bonus, job change), whenever fixed commitments change (new mortgage, rent rise, car replacement), whenever a spending category exceeds 125% of budget for three consecutive months (signal of unrealistic target rather than willpower failure). Budgets from two years ago are usually already wrong. The discipline is revisiting, not holding a pattern indefinitely.

What this calculator shows

The tool lets you allocate income across categories and check the percentages. It doesn't track actual spending (that requires a separate system — app, spreadsheet, or bank-integrated tool). Use this for the planning step; use a tracker for the execution step. The two work together; neither alone is enough.