This burn rate calculator estimates how fast a business is consuming its cash and how long the current balance will last. It works from either a multi-month history of operating cash flows or from two balance snapshots, and it reports gross burn, net burn, burn percentages, and cash runway.
What Is Burn Rate?
Burn rate is the speed at which a business spends its cash. In finance it is usually expressed as an average monthly amount over a defined period — the amount by which operating outflows exceed operating inflows each month. Startups and small businesses track burn rate closely because it directly determines how long the current cash balance will last before more capital is needed.
Burn rate is a cash concept, not an accounting one. It measures actual cash leaving the business, not the accrual-based losses recorded on an income statement. A business can report a profit on paper while burning cash, and the reverse is also possible. What limits a company in practice is usually cash, not profit — which is why burn rate is one of the most-watched numbers in financial planning.
Gross Burn Rate vs. Net Burn Rate
These two figures answer different questions.
Gross burn rate is total operating cash spent per month — payroll, contractors, rent, software, marketing, and other operating outflows. It describes the cost to run the business at its current scale without considering any money coming in.
Net burn rate is gross burn minus operating cash inflows. It describes how much cash the business is actually consuming after revenue and other operating receipts. A company with high gross burn and strong inflows can have low or negative net burn; a company with modest gross burn and no inflows can have a high net burn.
The calculator reports both, because each serves a purpose. Gross burn tells you the operating footprint; net burn determines runway. The Gross vs net burn chart visualises the two side by side for the average month — how much of your operating outflows is covered by inflows, and how much of the remainder is being drawn from cash reserves.
How to Calculate Cash Burn Rate
The most common approach is monthly averaging: divide the total operating outflows over a period by the number of months in that period.
- Gross burn: total operating outflows ÷ number of months.
- Net burn: gross burn − average monthly operating inflows.
Using a multi-month average smooths out monthly variance, so a heavy hiring month or a slow revenue month does not dominate the result. One or two months is enough for a quick check; three to six months gives a more stable average, especially for businesses with irregular revenue.
When only two cash balance snapshots are available, the calculation simplifies to (starting cash − ending cash) ÷ months. That produces the average net cash change, which is approximately net burn when no financing occurred in the period. The calculator's start/end mode lets you adjust for financing so the result reflects operations rather than funding.
Cash Burn Rate Formula
For monthly cash-flow mode:
- Gross burn = total operating outflows ÷ months
- Average operating inflow = total operating inflows ÷ months
- Net burn = gross burn − average operating inflow
For start/end mode:
- Average cash change = (start cash − end cash) ÷ months
- Operating net burn = (start cash − end cash + net financing raised) ÷ months
A worked example. A business has $500,000 cash on hand. Over three months it took in $30,000, $45,000, and $50,000 of operating inflows, and paid out $180,000, $195,000, and $190,000 of operating outflows.
- Total inflows = $125,000 → average monthly inflow ≈ $41,667
- Total outflows = $565,000 → gross monthly burn ≈ $188,333
- Net monthly burn ≈ $188,333 − $41,667 = $146,666
- Estimated runway ≈ $500,000 ÷ $146,666 ≈ 3.4 months
The runway figure assumes the average holds constant — a planning assumption, not a prediction.
Monthly Cash Burn and Burn Rate Trends
A single monthly figure can hide a lot. Reviewing several months together often shows that one-off expenses — a legal bill, a tax payment, a large equipment purchase — are inflating one month and making the average look worse than the underlying trend. It can also show the opposite: a revenue spike masking a steadily rising cost base.
The calculator's monthly table and trend chart make these patterns visible. If one month contains a large one-time charge, the optional one-time expense field lets you exclude it from the average while still showing it in the totals — a useful way to compare normalized burn against actual cash use.
Burn Rate Percentage
Burn as a percentage of available cash — net burn ÷ cash balance × 100 — is a quick way to compare cash consumption across periods or across companies of different sizes. A 5% monthly burn consumes a twentieth of the cash each month; a 20% monthly burn consumes a fifth. All else equal, a lower percentage implies a longer runway.
The percentage has limits. It depends entirely on the denominator — the current cash balance — so a business that raised a large round will show a much lower burn percentage than an otherwise identical business with less cash. It says nothing about revenue, profitability, or whether the burn is funding productive growth. Use it as one input, not a verdict.
Burn Rate and Cash Runway
Cash runway is how long the current cash balance will last at the current net burn. It is the number most founders actually care about, and it is derived directly from the two figures above:
Cash runway (months) = available cash ÷ net monthly burn
Two conditions have to hold for runway to be meaningful: the cash balance must be positive, and net burn must be positive. If net burn is zero or negative, the business is not depleting cash from operations and runway is not limited by burn. The calculator surfaces that case explicitly rather than reporting an infinite runway.
Runway is a projection, not a forecast. It assumes average net burn stays constant. In reality, burn usually changes — hiring, seasonality, pricing changes, and new contracts all shift the number. A more conservative runway estimate uses a higher burn than the historical average; a more optimistic one assumes revenue growth reduces net burn over time.
The Runway health chart plots the estimated runway against two soft planning thresholds — six months (critical) and twelve months (buffer) — with colour-coded zones to make the result easier to interpret at a glance. Six months is a common reference point for the point at which cutting burn or securing cash becomes urgent; twelve months is a common buffer target because it allows time for a fundraising cycle, which typically runs three to six months. These are widely used planning reference points, not universal rules — a business with a longer fundraising window or a faster path to profitability may reasonably treat different numbers as critical.
Cash Runway Analysis for Startups
Founders commonly use runway analysis to answer three questions: how much time do we have, how much do we need to change to extend it, and when should we start raising. Calculating runway from the current cash balance and average net burn gives a baseline for all three.
A straightforward planning pattern is to compare runway against the time it takes to raise a round — typically three to six months from first conversation to cash in the bank. If runway is shorter than that window, the practical answer is either to reduce burn, extend the raise timeline, or start the process earlier than feels necessary.
There is no universal "good" burn rate. The right burn depends on the business's cash reserves, its stage, its growth rate, its operating costs, and what it is trying to accomplish. A pre-revenue company with significant runway may reasonably run a high burn to reach a milestone; a profitable business with thin reserves may want to keep burn near zero. The number is a planning input, not a grade.
Common Calculation Mistakes
- Confusing cash burn with accounting loss. A business can show a loss on the income statement while cash is unchanged, or a profit while cash falls sharply. Burn is a cash concept and should be calculated from cash movements, not accrual figures.
- Counting financing as operating inflow. A funding round, a new loan, or a credit draw is not operating revenue. Including it makes net burn look artificially low and overstates runway. The start/end mode's financing adjustment exists to keep the two separate.
- Double-counting expenses. If you enter a total outflow and also enter the same expense in a cost breakdown, the outflow is counted twice. Use one or the other.
- Ignoring one-time movements. A tax payment, a legal settlement, or a large annual software renewal can distort a monthly average. Either exclude it explicitly (via the one-time field) or use a longer averaging window.
- Treating the historical average as a forecast. Burn rate describes what happened. Extending it forward assumes the average holds — a reasonable starting point, but one that should be adjusted for known upcoming changes.
