Ask ten owners how much cash their business should keep on hand and you will get ten different answers, most of them guesses. Some keep almost nothing and sweat every payroll. Others hoard so much that the business quietly starves itself of growth. The real question is not "how much cash?" It is "how much cash runway?" That is, if revenue slowed or stopped tomorrow, how many months could your business keep operating before the account hit zero?
Most owners have never calculated it. The data says the answer is uncomfortable: research from the JPMorgan Chase Institute, based on the actual bank activity of nearly 600,000 small businesses, found the median business holds only about 27 days of cash buffer. Not months. Days. One slow month, one big client paying late, one surprise repair, and half of American small businesses are in trouble.
This post shows you how to calculate your runway in ten minutes, how to set a target that fits your business instead of a generic rule of thumb, and how to build toward it without choking off growth.
Key Takeaways
- Cash runway = cash on hand divided by average monthly operating outflows. It answers "how many months could we survive?"
- The median small business holds roughly 27 days of buffer. Most CFOs want to see 3 to 6 months, adjusted for your revenue model.
- Recurring revenue and low fixed costs justify a smaller reserve. Lumpy, project-based, or seasonal revenue demands a bigger one.
- Too much cash is a real problem too: money sitting idle is money not going to growth, debt paydown, or your own pocket.
- Build runway with a separate reserve account, a monthly transfer you treat like a bill, and a forecast that warns you before you need it.
What Cash Runway Actually Means
Cash runway is the number of months your business could keep paying its bills if cash stopped coming in. The math is simple:
The calculation
- Start with total cash available: operating account, savings, and any truly unused line of credit you could draw (count the credit separately; it is borrowed runway, not owned runway).
- Find your average monthly cash outflow: add up the last 6 months of total money out (payroll, rent, software, loan payments, owner draws, everything) and divide by 6.
- Divide cash by monthly outflow. That is your runway in months.
If you have $80,000 in the bank and the business burns $40,000 a month, you have two months of runway. Simple, and sobering for most owners who run it the first time.
Why "months of cash" beats a dollar target
A flat number like "keep $50k in the bank" means very different things to a $500k business and a $5M business. Months of runway scales with you. It is also the number a lender, buyer, or investor will mentally calculate the moment they see your balance sheet, so you should know it before they do.
How Much Is Enough? The Honest Answer
The standard advice is 3 to 6 months of operating expenses. That range is a decent starting point, but the right number for your business depends on how predictable your cash actually is.
When you can live near 3 months
- Revenue is recurring or contracted: retainers, subscriptions, long-term service agreements.
- Your customer base is diversified, with no single client over 15 to 20% of revenue.
- Costs are flexible: contractors you can scale down, month-to-month commitments, low fixed overhead.
- You have a proven, committed line of credit as a second layer of defense.
When you should hold 6 months or more
- Revenue is project-based or lumpy: construction, agencies with big one-off engagements, anything bid-driven.
- The business is seasonal, and the reserve has to carry you through the slow stretch. If that is you, the reserve target should be built around your specific trough, which we cover in how to manage seasonal cash flow.
- One or two clients dominate revenue, so a single loss cuts deep.
- Payroll is a large, fixed share of monthly outflows and you cannot flex it quickly.
- You are mid-transition: launching a location, changing your model, or absorbing a key-person risk.
Notice what is not on either list: your industry's average. What matters is your volatility, your concentration, and your ability to cut costs fast.
Yes, You Can Hold Too Much Cash
This surprises owners, but a bloated reserve is a quiet form of waste. Every dollar beyond your target is a dollar earning almost nothing while it could be:
- Funding growth: marketing, equipment, or a hire with a clear payback period.
- Paying down expensive debt, which is a guaranteed return equal to the interest rate.
- Coming home to you as an owner distribution. The business is supposed to pay you, not just employ you.
A useful discipline: set a target range, not a single number. Say, 4 to 5 months of outflows. Below the bottom of the range, you pause discretionary spending and rebuild. Above the top, you deliberately deploy the excess. Cash stops being an emotional comfort blanket and becomes a managed asset.
How to Build Runway Without Starving the Business
If you are at 27 days like the median business, jumping to 4 months feels impossible. It is not. It is a 12 to 18 month project done in small, boring steps.
The mechanics
- Open a separate reserve account. Money mixed into the operating account gets spent. Out of sight is the whole point.
- Set a monthly transfer and treat it like rent. Even 2 to 3% of revenue compounds fast. A $2M business moving 2.5% builds over $4,000 a month.
- Sweep windfalls. When a big invoice lands or a strong month closes, move a set percentage of the surplus before it blends into the balance.
- Attack the number from both sides. Faster collections and trimmed expenses both extend runway without a single new dollar of revenue.
Know your number before you need it
A reserve tells you how long you can survive. A forecast tells you whether you will have to. Pair your runway target with a rolling 12-month cash flow forecast so you can see the tight months coming two or three quarters out, while there is still time to act. Owners who get in trouble almost never lacked options. They lacked warning.
The CFO's View: Runway Is a Strategy Number
Here is the mindset shift. Cash runway is not just insurance against disaster. It is what buys you the ability to make good decisions slowly. With 30 days of cash, you take the bad client, the discounted project, the expensive loan, because you have to. With five months, you can negotiate, wait, and choose. Every strategic option your business has, from hiring ahead of growth to walking away from a bad deal, is priced in months of runway.
This is exactly the kind of number a CFO watches for you every month: where runway sits today, where the forecast says it is heading, and what to do about the gap. That ongoing visibility is the core of our CFO Navigator service, where we keep the forecast current so you are never surprised by your own bank account.
Conclusion
Calculate your runway this week; it takes ten minutes and one bank statement. Set a target range that reflects how volatile your revenue really is, not a borrowed rule of thumb. Then build toward it with a separate account and a monthly transfer you never skip, and pair it with a forecast so the reserve is a tool you plan with, not a parachute you discover too late. The median business is running on 27 days. You do not have to be the median.