How do I calculate monthly cash flow for a small business?

Subtract your total monthly expenses (fixed costs plus variable costs) from the cash actually collected that month. Account for accounts receivable lag — if customers pay 30 days late, only a portion of your monthly revenue arrives as cash in the same period.

What is a good cash flow for a small business?

Any positive net cash flow is healthy — it means the business generates more cash than it spends. Most advisors recommend building 3–6 months of operating expenses in cash reserves as a buffer against slow months or unexpected costs.

How many months of runway should a small business have?

At least 3–6 months of runway is the standard recommendation. Under 2 months is considered critical — at that point, cutting costs or securing a line of credit should be the immediate priority.

SmartBizCalc

Cash Flow Calculator

See your monthly net cash flow, 3-month projection, and how long your cash reserves will last — accounting for payment collection delays that most calculators ignore.

Revenue

Monthly Revenue ($)

AR Collection Lag (days)

Monthly Growth Rate (%)

Cash on Hand ($)

Fixed Costs (same every month)

Rent / Mortgage ($)

Payroll ($)

Loan Payments ($)

Other Fixed ($)

Variable Costs (scale with revenue)

COGS / Materials ($)

Marketing / Ads ($)

Other Variable Costs ($)

Monthly Cash Flow

Cash In (collected this month)—

Total Fixed Costs—

Total Variable Costs—

Total Cash Out—

Net Cash Flow—

3-Month Projection

Month 1 Net—

Month 2 Net—

Month 3 Net—

Cumulative Cash Position—

Cash Runway

Cash on Hand—

Runway (at current burn)—

Projections assume consistent costs and the stated growth rate. AR lag reduces cash collected vs. revenue earned. This is a planning tool — consult your accountant for formal cash flow statements.

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You might also find useful: Break-Even Calculator · Profit Margin Calculator · Startup Cost Calculator