Cash Flow Calculator

See exactly what flows in versus out each month — for personal finances, small business, or rental property.

Monthly Income

Monthly Expenses

Results

$6,000
Total Income
$4,150
Total Expenses
$1,850
Net Cash Flow
30.8%
Cash Flow Margin
Cash Flow Margin30.8%

What is cash flow?

Cash flow is the difference between money coming in and money going out. Positive means you're saving each month. Negative means you're drawing down — a signal to adjust your budget or income.

Cash Flow = Total Income − Total Expenses
Cash Flow Margin = (Cash Flow ÷ Total Income) × 100

For personal finance, 20%+ cash flow margin is a solid target. For rental property, 30–40% is the range where the investment typically pencils out.

How it works

This calculator breaks your cash flow into three distinct lenses: personal monthly income and expenses, business revenue and costs, and residential rental property income and costs. Adding them together gives you a single net cash flow number that shows whether money is coming in or going out each month.

Net Cash Flow = (Personal Income − Personal Expenses) + (Business Revenue − Business Costs) + (Rental Income − Rental Costs)

Positive means you are saving or generating surplus. Negative means you are drawing down reserves. The deeper the red, the more urgent a budget review.

Business costs are often underestimated

When entering business figures, include all true costs — payroll taxes, software subscriptions, and seasonal variation. This prevents the common mistake of celebrating "profit" that quietly evaporates within weeks.

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For educational purposes only. Not financial or business advice.

Understanding net cash flow: more than just profit

Cash flow and profit are often confused, but they tell different stories. Profit is an accounting concept — it includes non-cash items like depreciation and amortization, and it follows accrual recognition rules that may not reflect when money actually changes hands. Cash flow, by contrast, tracks the real movement of money in and out of your account. A business can show a profit on paper while still struggling to make payroll. Conversely, a rental property might show a modest loss on paper while generating positive monthly cash flow after accounting for mortgage principal paydown and non-cash depreciation.

Cash flow vs. profit: why the distinction matters

The cash flow formula is straightforward:

Net Cash Flow = Total Cash Inflows − Total Cash Outflows

For a small business, inflows include revenue from sales, loans, and investment. Outflows cover rent, payroll, supplies, loan payments, and owner draws. For a rental property, inflows are primarily rent and any ancillary income like parking or laundry. Outflows include the mortgage payment, property tax, insurance, maintenance, property management, and a vacancy allowance. The resulting number — positive or negative — tells you whether your operation is self-sustaining or drawing from reserves.

Interpreting positive and negative cash flow

A positive cash flow number means your inflows exceed your outflows for the period. That surplus can be saved, reinvested, or used to pay down debt faster. It is a signal of financial health and operational efficiency. A negative cash flow number means you are spending more than you are taking in. This is not always a crisis — a new business may legitimately run negative for months while building inventory and client relationships, and a rental property purchased with a large down payment may still show negative cash flow while appreciation and principal paydown build equity. However, prolonged negative cash flow without a clear strategy is a warning sign that should prompt either expense reduction or revenue increase.

Cash flow margin as a benchmark

A cash flow margin below 10% gives you little buffer for unexpected repairs, seasonal downturns, or economic shifts. Aim for 20%+ in personal finances, and 30–40% in rental property, to build meaningful resilience.

Practical tips to improve your cash flow

Improving cash flow usually comes down to one of three levers: increase inflow, reduce outflow, or do both simultaneously. On the income side, small businesses can renegotiate contracts, add higher-margin products or services, or collect receivables faster with early-payment discounts. Rental property owners can adjust rent to market rates, reduce vacancy by improving tenant retention, or add income streams like pet fees or storage fees. On the expense side, scrutinize recurring subscriptions, negotiate vendor contracts, and build a maintenance reserve so unexpected repairs do not create a cash crisis.

For personal finances, automate savings so that surplus cash flow does not silently disappear into discretionary spending. Treat your cash flow buffer as a non-negotiable expense, not an afterthought.

Worked example: rental property cash flow

Consider a single-family rental with monthly rent of $2,000. The mortgage (principal and interest) is $1,200, property tax is $200 per month, insurance is $150, HOA fees are $50, routine maintenance is $150, and a vacancy allowance is set at $100 to account for occasional empty months. Property management is not used, so that cost is $0. Other expenses total $50.

Cash Inflows: $2,000 (rent)
Cash Outflows: $1,200 + $200 + $150 + $50 + $150 + $100 + $50 = $1,900
Net Cash Flow: $2,000 − $1,900 = $100/month

This property generates a modest positive cash flow of $100 per month — a 5% cash flow margin. While this is positive, it leaves little room for unexpected furnace replacement or a prolonged vacancy. A landlord in this position might look to increase rent at renewal, shop for a lower mortgage rate, reduce the vacancy allowance through better tenant screening, or trim discretionary repairs to improve the margin toward the 30–40% target range.

Use this calculator to model your own numbers — adjust the inputs and see how changes in rent, expenses, or loan terms shift your net cash flow and margin in real time.