Cash Flow Calculator
See where your monthly income actually goes, how your spending compares to the 50/30/20 guideline, and how many months of expenses your emergency fund really covers.
Income
Essential Spending
Discretionary Spending
Saving
Results
Enter your income and monthly spending to see your surplus, your real savings rate, and where you sit against the 50/30/20 guideline.
Figures are whatever you enter, and most people underestimate discretionary spending when working from memory rather than from statements. Nothing is stored or transmitted; this runs entirely in your browser.
The number that matters is the surplus
Budgets fail because they are built as a list of restrictions. Cash flow planning works better because it asks one question: what is left at the end of the month, and does it have a job?
Unassigned surplus is the most reliably spent money in any household. If the calculator shows a healthy figure left over each month and your savings balance is not growing by roughly that amount, the surplus is leaking somewhere. That gap between what you think you save and what you actually save is the single most common finding when we look at a real set of statements.
This is why the tool reports two savings rates. The first counts only deliberate saving and extra debt paydown. The second adds whatever is left over. If those two numbers are far apart, the second one is probably fiction.
About the 50/30/20 guideline
Half of take-home pay to needs, 30% to wants, 20% to saving and debt paydown. It is a useful starting frame and a poor destination, so treat the comparison as a diagnostic rather than a target.
Two situations where it breaks down honestly. In an expensive housing market, a 50% needs allocation may simply not be achievable, and forcing it means either a long commute or a worse house rather than a better financial position. And for a high earner, 20% saving is far too low: once needs are covered, the percentage available to save should climb well past it. The guideline compresses toward the middle, which is exactly where it is least useful.
What the split does do well is show you which of the three is out of proportion. Most people are surprised by the wants figure rather than the needs figure.
Emergency fund, measured properly
The usual advice is three to six months of expenses, and the important word is expenses, not income. The calculator measures your fund against your actual essential and discretionary spending, since that is what you would need to cover if income stopped.
- Three months is a reasonable floor for a dual-income household with stable, salaried work.
- Six months is the better target for a single earner, a commission or bonus-heavy income, or anyone self-employed.
- Beyond six months, cash starts costing you. Money held past a genuine reserve is usually better invested, and the exception is a known upcoming expense.
If your fund is short, it takes priority over almost everything except capturing a full employer retirement match. Without a reserve, an ordinary setback becomes credit card debt, and that undoes far more than the interest you earned by holding cash.
Where this fits
Cash flow is the foundation the rest of a plan sits on. Our cash flow management guide covers the business owner version of this problem, where personal and business money mix and income arrives unevenly. If you are working toward a specific target rather than general saving, the savings goal calculator takes the surplus this tool identifies and tells you whether it is enough.
Cash flow questions
What is a good savings rate?
Fifteen percent of gross income is a common floor for someone starting in their twenties, and the required rate rises sharply the later you begin. For higher earners the guideline understates what is achievable: once essential spending is covered, the percentage available should climb well above twenty percent. The more useful test is whether your savings balance grows each year by roughly what you believe you are saving.
Is the 50/30/20 rule actually useful?
As a diagnostic, yes. As a target, less so. It compresses toward the middle, which is where it is least informative. In an expensive housing market a fifty percent needs allocation may simply not be reachable, and for a high earner twenty percent saving is too low. What the split does well is show which of the three categories is out of proportion, and most people are surprised by the wants figure rather than the needs figure.
How much should I keep in an emergency fund?
Three to six months of expenses, and the important word is expenses rather than income. Three months is a reasonable floor for a dual-income household with stable salaried work. Six months suits a single earner, a commission or bonus-heavy income, or anyone self-employed. Beyond six months, cash starts costing you, and the money is usually better invested.
Why is my surplus not showing up in my savings?
This is the most common finding when we look at real statements. Unassigned surplus is the most reliably spent money in any household. If the calculator shows a healthy figure left over each month and your balances are not growing by roughly that amount, the money is leaking into spending you have not accounted for. Automating the transfer on payday is the usual fix.
Should I pay off debt or build savings first?
Generally: capture any full employer retirement match, then build a starter emergency fund, then attack high-interest debt, then return to saving. The match is an immediate guaranteed return that nothing else matches. Without a reserve, an ordinary setback becomes new credit card debt, which undoes more than the interest saved by paying down early.
Does the calculator store my figures?
No. Everything runs in your browser. Nothing is submitted, stored, or transmitted, and refreshing the page clears it.
Related tools and reading
The pieces that sit either side of this one.
Cash Flow Management
The business owner version: separating business capital from personal income, and planning through uneven months.
Read the guide →Savings Goal Calculator
Take the surplus this tool finds and see whether it is enough to hit a target by a deadline.
Open the tool →Net Worth Calculator
The other half of the picture: what all of this monthly activity has actually built.
Open the tool →