How the budget planner works
Last updated 10 November 2026
A budget is a plan for your monthly income. This planner adds up everything you earn, everything you spend and everything you set aside, and tells you what is left over or how far short you fall.
Start with the income lines. Enter what reaches your bank account, and say how often. Then list your costs. Each line has a category, a frequency and a type. The type matters: fixed costs stay the same every month, variable costs move around, and saving is money you pay to yourself, such as a retirement annuity or an emergency fund.
How the numbers are worked out
- Per month: every amount is converted to a monthly figure. A weekly amount is multiplied by 52 and divided by 12.
- Total spending and saving: the sum of every line, including savings.
- Left over: total income minus total spending and saving.
- Disposable income: total income minus fixed costs. It is the money you can still decide about.
- Savings rate: money marked Saving, as a share of total income.
Worked example
The starting figures are examples, not averages. They show an income of R 30 000 a month and spending and saving of R 28 200.
- Fixed costs are R 17 200 and variable costs are R 8 000.
- R 3 000 goes into savings and retirement, which is a savings rate of 10.0%.
- Left over: R 30 000 − R 28 200 = R 1 800 a month.
- Disposable income: R 30 000 − R 17 200 = R 12 800.
How to read your result
Left over is the quickest check. A positive figure means your plan balances on paper. A negative figure means the lines you entered add up to more than you earn, so a cost, an amount or the income needs another look. With the starting figures, left over is R 1 800 a month.
Next, look at the split between fixed and variable costs. Fixed costs are hard to change in the short term, so a large fixed share leaves less room to adjust if your income drops. Variable costs are where small changes show up first. Disposable income is useful for the same reason: it is what remains after the fixed costs, before variable spending and saving.
A closer look at the savings rate
The savings rate counts only the lines you mark as Saving, as a share of total income. A line marked fixed or variable is not counted, even if the money builds your wealth, such as an extra payment into a bond. How you mark each line is up to you, so two people with the same budget can show different rates.
Common mistakes
- Entering gross salary. The planner needs the amount that reaches your account.
- Leaving out cash spending, such as taxis, airtime, takeaways and small shop purchases. They add up over a month.
- Entering a once-off bonus as if it arrives every month.
- Counting the same money twice, for example a debit order that also appears under another category.
What this does not cover
The planner is a plan, not a record. It does not read your bank account, track what you actually spend or remember anything between visits. It also does not work out tax, change amounts for inflation or look ahead beyond one typical month. Compare the plan with your statements from time to time and adjust the lines yourself.
Things to watch
- Annual costs such as insurance, licence renewals and school fees are easy to forget. Add them with the Yearly option so they are spread over twelve months.
- Irregular income should be entered as a conservative monthly figure.
- Categories you type yourself are grouped by name, so spell them the same way each time.
- The planner works with the figures you give it. It does not check them or give advice. See the disclaimer.
For a longer view, try the savings goal calculator or see what a retirement contribution does to your tax with the retirement annuity tax calculator.