Runway is a date, not a number of months

The months figure is an average of a future that is not average. The date is the thing an owner can act on, and it usually arrives earlier.

An owner can usually say roughly how many months of cash are left. Naming the month is a different question, and the two answers are not the same number. They are different numbers, and the second one is almost always earlier than the first, because the shortcut that produces the months figure assumes every month ahead looks like this one. No month looks like this one. Insurance renews. Inventory gets reordered. Revenue grows, which helps, and a supplier moves to shorter terms, which does not.

This article works one example all the way through so the gap is visible rather than asserted. The claim is narrow: months is the wrong unit for a decision, and the date is the right one.

The shortcut and what it hides

The usual calculation is cash divided by net burn.

Take a store with $84,000 in the bank. Fixed costs are $31,500 a month, which is payroll, software, rent and the retainers that do not move with volume. Revenue is $46,000 a month at a 38 percent contribution margin, so the business contributes $17,480 a month toward those fixed costs.

Net burn is $31,500 minus $17,480, which is $14,020 a month. Divide $84,000 by $14,020 and the answer is 5.99 months.

Call it six months. Six months from the first of September puts the problem at the end of February, which is far enough away to feel like next quarter's problem. That is exactly the feeling the number is producing, and it is wrong.

The same business, month by month

Two ordinary things happen. An inventory reorder of $12,000 lands in October, and the annual insurance renewal of $9,400 lands in November. Revenue grows 4 percent a month, which is real growth and helps.

Everything needed to redo this is above: $46,000 of revenue growing 4 percent a month at a 38 percent margin, against $31,500 of fixed costs, starting from $84,000.

Cash goes below zero in January, not at the end of February. The shortcut was out by about four weeks, and it was out in the direction that costs the most, because four weeks is roughly the difference between having time to fix something and not having it.

Notice what did the damage. Growth was real and it helped every single month. The two one off payments were not surprises, they were known, scheduled, ordinary business. They were simply invisible to a calculation that multiplies one month by six.

Payroll clears before the month ends

The table above says January, and January is still optimistic, because a business does not fail on the last day of a month. It fails on the day a payment it has committed to leaves the account.

Payroll clears on whatever day your cycle sets, and supplier terms land on their own dates. If the account is going to be short by $223 at the end of January, then in practice the shortfall arrives with whichever payment happens to be scheduled first, and that is whichever committed payment falls first inside that month, not the last day of it.

So the honest version of the answer is not "about six months". It is "the last comfortable payment run is in December, and the one after it is the problem."

Why the months number persists

Because it is easy, and because it is directionally reassuring in a way the date is not.

There is also a subtler reason. A months figure feels like a property of the business, something stable and describable, the way a margin is. A date feels like a deadline, and a deadline demands a decision. The shortcut is not just less accurate, it is less demanding, and the two things are related.

There is no public figure here for how many owners can name their date rather than their months. None is cited because none was found that could be stood behind, and inventing one to make the point land harder would undo the point.

What changes when the unit changes

A months figure supports one kind of conversation, which is whether things feel tight. A date supports the conversations that actually move a business.

Hiring. The question stops being whether the business can afford a person and becomes whether the person is producing contribution before the date. A hire in October that pays for itself by January is a different decision from the same hire if the date is November.

Discounting. A promotion that trades margin for volume is a good idea or a bad one depending on whether the cash lands before or after the date. Months cannot answer that. A date can.

Raising or borrowing. Facilities take weeks to arrange and the good ones take longer. Working backward from a date tells you the week to start. Working from a months figure tells you to start soon, which nobody has ever acted on.

Supplier terms. Moving one supplier from 15 days to 30 shifts a payment across a month boundary. On a months figure that change is invisible. On a dated cash curve it can be worth more than a price negotiation.

The one case where a short runway is not the emergency

A short date is not automatically a crisis. It is a crisis when the business is also unprofitable at the contribution line, because then time is the only thing being bought.

If contribution is positive and growing, a short date is a timing problem, and timing problems have more solutions than profitability problems do. The example above is one of these. That business contributes more every month and is losing to fixed costs and to two scheduled payments. It does not need a different business model, it needs the December decision made in September.

Telling those two situations apart is the whole value of building the curve rather than the ratio.

What to do this week

1. Write down the actual cash balance, not the balance minus what you owe in your head. One number, from the account.
2. List fixed costs as they leave, with the day of the month each one goes. Payroll, software, rent, retainers, loan payments.
3. List the next six months of known one offs. Insurance renewals, annual software, tax payments, inventory reorders, equipment. These are the items the shortcut deletes, and they are all already knowable today.
4. Build the running balance forward and mark the first month it goes below zero. That month is your answer. Then move it back to the last payment date that falls before it, and use that.
5. Write the date on the same page as your three biggest planned spends. Any spend after the date is not a plan, it is a wish.

This is arithmetic you can check, not accounting or financial advice. The numbers above are a constructed example, not a client, and your own figures are the only ones that decide anything.

Runway and Burn does the first half of this in the browser: put in cash, fixed costs, revenue and your variable cost percent, and it returns the net burn, the months figure, the calendar month the runway ends, and the revenue needed to break even. It compounds growth month by month, so its date is already better than dividing cash by burn. It does not take one off payments, so the reorder and the renewal above are still yours to add at step three. Run the tool first, then subtract your one offs from the curve it draws.

And if the date you get back is comfortable, and the thing capping the business is how many hours you personally have rather than how much cash it has, that is the one situation where a full time operations seat is worth twenty minutes of your time to discuss. If the date is close, a seat is another fixed cost landing before it, and the honest answer is revenue or cuts instead.