Runway is a decision clock, not a countdown
The number matters because of when it forces your hand, not when it ends. Hiring, signing a lease, taking a big contract that needs materials up front — those decisions get made months before the money runs out. A useful rule is that you should know your runway before every commitment that changes it.
Borrowed months are not owned months
The chart separates the three layers deliberately. Business cash is yours. Personal reserve is your family's, and injecting it converts a business problem into a household one. Credit is someone else's money that has to be repaid on their schedule, usually with a personal guarantee attached, and a line of credit can be reduced or pulled by the lender at the moment you most need it. Counting all three as one number is how owners talk themselves into being comfortable.
The median small business runs on 27 days of cash
Research from the JPMorgan Chase Institute, covering hundreds of thousands of small businesses, found the median holds enough cash to survive 27 days without any money coming in. That's not a target — it's evidence that most owners are operating with far less cushion than they'd guess. Labor-intensive businesses tend to hold even less. If your buffer days figure above is in that neighborhood, you're normal, and normal is thinner than it should be.
What actually extends runway
Fixed costs are the lever with the most leverage, because they don't shrink when revenue does. A dollar cut from fixed costs extends runway further than a dollar of new revenue, since revenue arrives with variable costs attached.
Getting paid faster doesn't show up in this model but changes everything in practice. Runway is about cash timing, not profitability — a profitable business with 90-day receivables can still miss payroll.
Your own draw is often the fastest lever available, and the hardest. Cutting it buys months directly, but if it forces you to raid personal savings later you've moved the problem, not solved it.
Borrowing before you need it is the one that requires foresight. Lenders extend credit to businesses that don't obviously need it. The time to open a line is when the numbers above look comfortable.
What this model leaves out
It assumes revenue arrives as cash in the month it's earned, that costs are steady rather than seasonal, that variable costs stay a constant share of revenue, and that your credit stays available. It ignores receivables and payables timing, inventory, taxes, loan principal payments on existing debt, and any one-time expense you haven't put in the fixed-cost figure. Real cash flow is lumpier than any smooth curve, and most businesses that run out of money do so in a month they thought would be fine.
The best time to look at this is when it looks fine.
Runway decisions are easy at twelve months and nearly impossible at three. If the number above is shorter than you expected, or if you're not sure which lever to pull first, that's a conversation worth having now.
This calculator is provided by Cool Wealth Management for educational purposes only. It is not financial, accounting, tax, or legal advice, not a cash flow forecast prepared under any professional standard, and not a recommendation to borrow, to inject personal funds into a business, or to take any other action. Decisions about business financing and personal capital have consequences that depend on facts this tool does not capture.
The projection applies a single monthly growth rate to current revenue, holds fixed costs constant, treats variable costs as a constant percentage of revenue, and assumes all revenue is collected as cash in the month earned. It draws on business cash first, then personal funds, then credit, accruing interest monthly on drawn balances at the rate entered. It excludes accounts receivable and payable timing, inventory, seasonality, taxes, principal repayment on existing debt, capital expenditure, and any change in credit availability. Lenders may reduce or withdraw an undrawn line of credit, and undrawn credit should not be treated as equivalent to cash.
The reference to median cash buffer days reflects published research by the JPMorgan Chase Institute on the cash positions of small businesses and is included for general context only. It is not a benchmark, a recommendation, or a standard of adequacy for any particular business.
Cool Wealth Management is a registered investment adviser. Advisory services are only offered to clients or prospective clients where Cool Wealth Management and its representatives are properly licensed or exempt from licensure. Nothing here is personalized advice.