Cash flow
Budget and emergency fund calculator
Your surplus, your essential spending, and the gap to an emergency fund of the size you choose.
- No sign-up or email
- Runs in your browser
- Assumptions you can edit
- Print or save as PDF
What is left over each month, and how long until I have a buffer?
Two numbers matter here and they are different: everything you spend, and everything you would still have to spend if your income stopped. The second one sets the size of an emergency fund. Irregular annual bills are included as a monthly equivalent, because leaving them out is what makes a budget look balanced and then fail in the month the car registration falls due.
$
Applies to every expense line below.
$
Registration, excesses, school fees, gifts. Divided by 12 and treated as essential.
$
months
Your choice. This calculator does not recommend a number.
What you spend
$
$
$
$
$
$
$
$
$
Monthly surplus
$913
$6,933 in, $6,020 out
Essential expenses
$5,200
What you cannot stop paying
Emergency fund (3 months)
$15,600
$5,000 saved so far
Still to save
$10,600
About 1 year at the current surplus
| Where it goes | Per month | Share of income | Counted as |
|---|---|---|---|
| Rent or mortgage | $2,400 | 34.6% | Essential |
| Groceries | $900 | 13% | Essential |
| Everything else | $700 | 10.1% | Discretionary |
| Other loan and card repayments | $600 | 8.7% | Essential |
| Transport | $450 | 6.5% | Essential |
| Utilities | $350 | 5% | Essential |
| Irregular annual costs (spread over 12 months) | $300 | 4.3% | Essential |
| Insurance | $200 | 2.9% | Essential |
| Subscriptions | $120 | 1.7% | Discretionary |
Only essential lines count toward the emergency fund target. Irregular annual costs are divided by 12 and treated as essential.
Estimate only, based on the figures and assumptions you entered. It is general information, not financial advice, and it does not take your objectives, financial situation or needs into account. Model version 1.0.0, not independently reviewed.
Reading the result
What the numbers mean
Surplus is take-home income less everything, including the monthly share of irregular annual costs. If it is negative the calculator says so and does not offer a timeline.
Essential expenses exclude subscriptions and discretionary spending. The emergency fund target is a multiple of essentials, not of total spending, because the buffer only has to cover what you cannot stop paying.
Months to target assumes the whole surplus goes to the buffer and nothing interrupts it. Treat it as a best case.
Everything is converted to a monthly figure before anything is compared, so a fortnightly income and monthly rent are never subtracted from each other directly.
Worked example
An example, start to finish
$3,200 take-home per fortnight, monthly expenses as listed, $3,600 of irregular annual costs, $5,000 already accessible, three months of cover wanted.
- Monthly income
- $6,933
- Monthly expenses (incl. $300 irregular)
- $6,020
- Monthly surplus
- $913
- Essential expenses
- $5,200
- Emergency fund target (3 months)
- $15,600
- Gap after existing $5,000
- $10,600
- Time to close the gap
- About 1 year
The $3,600 of irregular costs adds $300 a month. Without it the surplus would look like $1,213 and the plan would break the first time an annual bill arrived.
Methodology
What this calculator assumes
Income and expenses are converted to monthly using the frequency you select: an annual figure is divided by 12, a fortnightly figure multiplied by 26 and divided by 12.
Irregular annual costs are divided by 12 and counted as essential.
Subscriptions and 'everything else' are treated as discretionary and excluded from the emergency-fund target. Every other line is essential.
The months of cover are entirely your choice. No default here is a recommendation.
Months to target divides the remaining gap by the current surplus, with no return earned on the balance along the way.
Limitations
What it does not do
Nothing is verified. The result is only as good as the figures you enter, and household spending is routinely underestimated — bank statements usually tell a different story from memory.
No bank connection, account linking or document upload. Everything is typed in and nothing leaves your browser.
Income is assumed steady. Variable, seasonal or commission income needs a different approach, and a larger buffer.
This does not model debt payoff order, offset strategy, or whether the surplus is better directed at debt, savings or super.
About this model
Built by the Souffle team. Model version 1.0.0, in effect from 2026-09-10. It has not been independently reviewed, and no review badge is shown for that reason. The calculation runs entirely in your browser — nothing you type is sent to us or to anyone else, and nothing is stored.
Questions
Common questions
How many months of expenses should an emergency fund cover?
That depends on job security, whether a household has one income or two, insurance cover and access to credit. Because the right answer is personal, this calculator takes the number from you rather than suggesting one.
Why is my surplus lower than I expected?
Most often the irregular annual costs line. Registration, insurance excesses, school fees and gifts are real spending that does not appear in a typical month, and spreading them over 12 months is the honest way to budget for them.
What if I am in deficit?
The calculator shows the shortfall and does not offer a timeline to an emergency fund, because there is no surplus to build one from. That is a genuine finding, not an error.
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