Guide, 2026-11-04

How to make a 50/30/20 budget spreadsheet (with a worked example)

Most budgets fail for the same reason: there are too many categories to keep in your head, so you never know whether the month is going well. The 50/30/20 rule fixes that by grouping everything into three buckets. Here is how it works and how to build a simple version in any spreadsheet.

What the 50/30/20 rule says

Take your after-tax income for the month (what actually arrives in your account) and aim to split it roughly like this:

• 50% needs: things you must pay to live and work. Rent or mortgage, groceries, utilities, insurance, transport to work, minimum debt payments.
• 30% wants: things you choose. Eating out, streaming, hobbies, holidays, most shopping.
• 20% savings: emergency fund, retirement contributions, saving for goals, and debt payments above the minimum.

It is a rule of thumb, not a law. In an expensive city, needs may be 60% or more; that is useful to know, not a failure. The value is in seeing your own split and deciding whether you are happy with it. You can set your own target percentages.

Step 1: List your categories and give each one a group

Make a sheet with three columns: category, group (Need, Want or Savings) and monthly budget. Keep it to 15-25 categories. Be honest with the group: a gym membership you rarely use is a want, not a need.

Step 2: Record every transaction

On a second sheet, one row per transaction: date, description, category and amount. Type them in or paste them from your bank's export, then assign the category. Enter refunds as negative amounts in the same category so they reduce that category's spending. Record transfers to savings as transactions in a savings category; that is what makes them count.

Step 3: Total each category for the month

Next to each category, total that month's transactions with a conditional sum, for example =SUMIFS(Amount, Category, A2, Date, ">="&Start, Date, "<="&End). Subtract the budget to get the difference. A positive difference means overspent.

Step 4: Total each group and divide by income

Sum the category totals by group with another SUMIFS on the group column, then divide each group by the month's income. Compare those three percentages with 50, 30 and 20.

Step 5: Work out what is left and your savings rate

Money left over = income − needs − wants − savings transfers. A simple savings rate is (savings transfers + money left over) ÷ income, but only if the left-over money actually stays saved. Moving it to savings at month end makes that true.

A worked example

A fictional household takes home $4,200 a month. The targets are $2,100 for needs (50%), $1,260 for wants (30%) and $840 for savings (20%). At the end of October:

The check: $2,310 + $1,050 + $630 + $210 = $4,200. Needs are over target, mostly because of rent, and savings are short. If the $210 left over is moved to savings, the savings rate becomes ($630 + $210) ÷ $4,200 = 20%, back on target.

The category view shows where to look next. Three categories went over budget this month:

Rent is hard to change quickly; these three are not. Together they are $270 over, more than the $210 savings gap.

Track the year, not just the month

One month can be distorted by an annual bill or a holiday. Add a month-by-month sheet with categories down the side and months across the top, plus a year-to-date column. If a category is over budget most months, the budget is probably unrealistic and should be raised, with something else lowered to match.

Common mistakes

• Using gross salary instead of take-home pay, which makes every percentage look better than it is.
• Counting money as "saved" just because it was not spent yet.
• Putting wants in the needs group so the split looks right.
• Forgetting irregular costs such as annual subscriptions, car repairs and gifts.
• Entering refunds as income instead of negative spending, which inflates both income and spending.

When a ready-made workbook saves time

The formulas above are not hard, but keeping month ranges, year-to-date totals and an over-budget ranking correct as the year goes on takes some care. SpendBook has these built in: budget vs actual for every category by month and year to date, the 50/30/20 check with your own targets, savings rate and the five categories most over budget. There is no bank connection, so you still type or paste transactions, and it is a budgeting tool, not financial advice.