How do you calculate cash runway for a business?

Cash runway is current cash divided by monthly burn: what you spend each month minus what you collect. With $48,000 in the bank and a $6,000 monthly burn, runway is 8 months. Burn is the real number to manage — every $1,500 you cut adds more than two months of runway.

What is the difference between burn rate and profit?

Profit counts revenue when it is earned and expenses when they are incurred; burn rate counts cash when it actually moves. A profitable business with net-60 customers can still burn cash every month if collections lag spending. That is why cash flow forecasts rank above profit forecasts for young businesses.

Why do profitable businesses run out of cash?

The timing gap: you earn revenue in one month, collect it one to two months later, and pay rent, payroll, and suppliers on fixed dates the whole time. Growth makes it worse because the gap grows with volume. Businesses run out of cash when they grow faster than their collections terms allow.

How far ahead should a small business forecast cash flow?

Ninety days is the practical standard: far enough to see the valleys and act, short enough that the projection is still built from real invoices and orders rather than guesses. Re-roll the forecast weekly and always flag the week with the lowest projected balance.

Business & Tax

Small Business Cash Flow Management: Runway, Burn, and the Timing Gap

Cash flow is a timing problem, not a profit problem. Burn rate, cash runway, the payment gap, and a 90-day forecast that keeps payroll safe.

By FreeCalculators Editorial · Published 2026-06-03 · Updated 2026-08-20 · 4 min read · 975 words

Small business cash flow is a timing problem, not a profit problem. A business can be comfortably profitable on paper and still run out of cash, because profit counts sales when they happen while cash counts them when they arrive. Chasing revenue you cannot yet collect is how healthy businesses die quietly in month nine.

Runway and burn rate

Burn rate is how much cash your business spends each month beyond what it brings in. Cash runway is how many months that burn can continue before the money runs out: current cash divided by monthly burn. The two numbers together tell you how much time you have to fix a shortfall.

Finding runway

                Cash in the bank = $48,000
Monthly revenue = $14,000
Monthly expenses = $20,000
Monthly burn = 20,000 - 14,000 = $6,000
Cash runway = 48,000 / 6,000 = 8 months
Cut expenses by $1,500 a month and burn drops to $4,500
Runway extends to 48,000 / 4,500 = 10.7 months

The timing gap

Most small business cash crises are the timing gap in disguise: you deliver work or ship goods, send an invoice with net-30 or net-60 terms, and wait weeks for the money while payroll and rent come due on fixed dates. The gap between earning and collecting is where the danger lives.

Earned money is not spendable money until it clears.
Bill	Amount	Due	Arrives in bank
Client invoice, net-30	$12,000	Day 30	Day 30-40 in practice
Client invoice, net-60	$8,000	Day 60	Day 60-70 in practice
Rent	$3,500	Day 1	-
Payroll	$6,000	Day 15 and 30	-

The 90-day forecast

A 90-day cash forecast is the single most useful financial document a small business keeps, and it needs no modeling talent. List every expected cash-in and cash-out for the next ninety days, week by week, then look for the valley. Fix the valley while it is still weeks away instead of discovering it on payday.

List known cash coming in: signed invoices with their real payment dates, expected sales, and any drawdowns or loans.
List every cash going out: rent, payroll, suppliers, taxes, insurance, and subscriptions — include dates.
Add the weekly totals to your starting balance to build the projected minimum balance across the quarter.
Flag any week below your comfort floor and act early: stretch a supplier, offer a small early-payment discount, or cut a subscription.

The levers that protect cash

When the forecast shows a shortfall, you have more levers than cutting marketing. Priority order roughly matches impact:

Shorten collections: invoice the day work completes, not weekly, and follow up on day five, not day thirty-five.
Collect deposits: 30 to 50 percent upfront on project work halts the worst of the timing gap immediately.
Negotiate terms: ask every regular supplier for net-45 instead of net-30 — cash sits with you longer by agreement, not accident.
Lean the inventory: every dollar in slow-moving stock is a dollar of runway you have converted into boxes.

Fund the gap before the gap bites

Fast-growing small businesses under-fund their timing gap more than their growth plan. If your runway dips below two months, act before the dip — a line of credit arranged while your cash is fine costs almost nothing to keep and is nearly impossible to arrange while it is critical.

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