Burn Rate & Runway Calculator
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Work out how many months of cash runway you have from your balance, monthly revenue and expenses — including gross burn, net burn and an approximate out-of-cash date. Runs entirely in your browser.
Burn rate and runway, defined
Burn rate is how quickly a company spends its cash reserves, and runway is how long those reserves will last at the current pace. Together they answer the single most important survival question for any pre-profit business: how many months until the money runs out?
There are two burn figures worth tracking. Gross burn is the total cash leaving the business each month — all operating expenses, payroll and overheads. Net burn nets out the cash coming in, so it reflects the actual erosion of your bank balance.
The formulas
The calculations are deliberately simple, which is exactly why they are trusted in board decks and investor updates.
- gross burn = monthly expenses
- net burn = monthly expenses − monthly revenue
- runway (months) = cash balance ÷ net burn
- If net burn ≤ 0 (revenue covers costs) the business is cash-flow positive and runway is infinite.
Why net burn drives the runway
It is tempting to divide your cash by gross burn, but that understates how long you can last whenever you have any revenue at all. Each dollar of revenue directly offsets a dollar of expense, so the meaningful number is net burn — the cash you actually consume after collecting sales.
The flip side is that revenue and expenses both move. A single strong month can flatter your runway, while a lumpy expense — an annual insurance bill, a big hire — can shorten it sharply. Use a representative average, and re-run the numbers whenever your cost base changes.
Using runway to make decisions
Most operators want to keep a comfortable cushion — commonly 12 to 18 months of runway — because raising capital or turning cash-flow positive both take time. When runway drops below six months without a clear plan, it is usually a signal to cut burn, accelerate revenue, or start a fundraise immediately.
Remember this tool gives a snapshot at today's rates. It assumes burn stays flat, which is rarely true for a growing company. Treat the out-of-cash estimate as a planning guide, not a guarantee, and pair it with a rolling cash-flow forecast for anything mission-critical.
Frequently asked questions
Should I include one-off expenses in monthly expenses?
For a steady-state runway estimate, use recurring monthly costs and spread large annual bills across twelve months. If a big one-off is imminent, model it separately or subtract it from your cash balance first.
My revenue exceeds my expenses — why does it show infinity?
Because you are no longer burning cash. When net burn is zero or negative your balance is not depleting, so there is no finite runway — the tool shows ∞ and your monthly net profit instead.
What counts as cash balance?
Use liquid funds you can actually spend — bank balances and cash equivalents. Do not include receivables you have not collected or credit lines you have not drawn.
How accurate is the out-of-cash date?
It projects today's net burn forward at a constant rate from the current month. It is an approximation for planning; real timing shifts as revenue and costs change.
How much runway should a startup keep?
A common rule of thumb is 12 to 18 months, because fundraising and reaching profitability both take longer than expected. Below six months is generally considered a danger zone that demands action.
Does the tool store my numbers?
No. All calculations happen locally in your browser and nothing is saved or transmitted.
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