Search “budget spreadsheet” and you’ll find templates with forty categories, colour-coded tabs for each month, and a cell for “gym — sub-category: swimming”. They’re lovely. They’re also abandoned by February, because their real cost isn’t money — it’s maintenance.

This guide builds the opposite: a budget with four numbers, one list, and one formula family. It’s an Excel lesson wearing a money costume — everything here comes straight from the path — and it survives real life because there’s almost nothing to maintain.

(The usual honesty note: this is arithmetic and spreadsheet craft, not financial advice.)

The four numbers

Every workable budget answers four questions:

# Number Meaning
1 In what lands in the account each month
2 Fixed what leaves whether you like it or not — rent/mortgage, council tax, energy, insurance, subscriptions
3 Flexible what you actually spent on living — food, fuel, fun
4 Future what moved to savings, ISA, pension top-ups, overpayments

If In − Fixed − Flexible − Future ≈ 0, you understand your month. That’s the whole game. Categories beyond that are decoration — add them later if the data earns it.

IN£2,400 FIXED£1,310 · leaves anyway FLEXIBLE£640 · the living FUTURE£450 · pays you later In − Fixed − Flexible − Future ≈ 0 → you understand the month
Four numbers. If they reconcile, the budget is doing its one job.

The build (20 minutes, honestly)

Sheet 1 — Spend. One Table, four columns: Date | What | Pot | Amount. Pot gets a drop-down allowing exactly three values: Fixed, Flexible, Future. Entering a line takes ten seconds, and the drop-down means totals can never be derailed by a typo.

Sheet 2 — Month. The four numbers:

=SUMIFS(Spend[Amount], Spend[Pot], "Fixed",
        Spend[Date], ">=" & $B$1,
        Spend[Date], "<"  & EDATE($B$1, 1))

…where B1 holds the first of the month. Copy the pattern for Flexible and Future, type your income above, subtract. (Every piece of that formula — the criteria pairs, the date brackets, the pinned $B$1 — is covered in the SUMIFS guide and the $ sign guide. This is where the path pays rent.)

That’s the entire system. No tab-per-month: months are just a filter on one long Table — which means next January you do nothing except keep typing rows.

Making it survive

  • Fill in weekly, not daily. Ten minutes on a Sunday with your banking app open. Daily budgeting is how February happens.
  • Don’t chase pennies. If the reconciliation lands within £20, you understand your month; move on. Precision is the enemy of persistence.
  • Watch the ratio, not the total. The interesting number over time is Future ÷ In — the share of the month that’s working for the later you. Even seeing it hover at 5% is knowledge most people never have.
  • Let categories emerge. After three months, a PivotTable on the What column ( you know how now) will tell you if a real category deserves splitting out of Flexible. Data first, categories second — the opposite of the 40-category template.

The spreadsheet isn’t the point. The point is that four numbers, honestly kept, beat forty categories abandoned — in budgets and, as it happens, in most things Excel touches.