Burn rate is the most quoted figure in early-stage companies and among the most loosely used. What it means depends on which of several definitions is being applied.
Gross and net measure different things
Gross burn is total cash spent in a period, regardless of income. It describes the cost of operating the company as currently structured.
Net burn subtracts cash received, so it describes how quickly the bank balance actually falls. A company with meaningful revenue can have high gross burn and modest net burn.
Quoting one while the listener assumes the other produces genuinely different conclusions, which is why the definition should be stated whenever the number is.
Runway is a projection, not a fact
Runway divides available cash by net burn to estimate remaining months. It assumes spending and income continue exactly as they are.
Neither assumption holds. Hiring increases burn ahead of the revenue it produces, and revenue rarely grows smoothly, so runway calculated today describes a scenario rather than a schedule.
Because fundraising takes months, the usable portion of runway is shorter than the calculated figure by roughly the length of that process.
Timing distorts the monthly figure
Annual payments, tax obligations and equipment purchases land in particular months, so a single month's burn can be unrepresentative in either direction.
Averaging over a quarter smooths this, though it can also hide a genuine trend if spending is rising steadily.
Cash timing differs from accounting periods as well, since invoiced revenue may arrive well after the work was recognised.
Low burn is not automatically better
Spending exists to buy progress. A company burning very little while making little progress is not in a stronger position than one spending more and advancing faster.
The useful comparison is burn against milestones reached, which is what determines whether the next round can be raised at all.
Efficiency measures pair burn with output
Investors commonly relate cash consumed to revenue added over the same period, which converts burn from a cost figure into a productivity one.
That ratio is more informative than either number separately, because it distinguishes a company investing in growth from one funding operations that are not compounding.
Read that way, burn stops being a number to minimise and becomes a description of how efficiently capital is being converted into progress.