Zero-based budgeting has one rule: income minus everything you plan to spend, save, or pay off equals exactly $0. Every dollar gets a job. You don't need an app, just a Google Sheet and five formulas.

1. SUM: total your income

=SUM(B2:B5) adds up take-home pay from every source. Use your lowest normal month if income varies.

2. SUMIF: total each category

=SUMIF(C:C,"Housing",D:D) adds every expense tagged "Housing". Repeat for Food, Transport, Savings, and so on.

3. The zero check

=B7-SUM(D2:D20) is income minus planned spending. The goal is 0. Positive means unassigned money, negative means overspending.

4. IF: a visual warning

=IF(B8=0,"Balanced","Fix me: "&TEXT(B8,"$0.00")) tells you at a glance whether the budget balances.

5. Percent of income

=D2/$B$7 shows what share of income each line takes.…