Burn Rate and Runway Calculator
How fast cash is leaving, how long it lasts, and what the revenue growth does to that.
Gross burn is what you spend each month.
How the burn rate and runway calculator works
Gross burn is what you spend each month. Net burn is spend minus revenue — the amount the bank balance actually falls by, and the one that determines runway.
Runway is cash divided by net burn. The flat version assumes nothing changes, which is never true, so this also projects month by month with your revenue growth applied. A company growing 10% a month can have materially more runway than the flat figure suggests, and one with flat revenue and rizing costs has less.
The convention worth knowing: raize when you have at least six months left, because a raize takes three to six months and negotiating from a short runway costs you the terms.
Formula: net burn = expenses − revenue; runway = cash / net burn
Worked examples
| Inputs | Runway | Note |
|---|---|---|
| 900k cash, 85k net burn, growing 8% | reaches break-even in month 14 before the cash runs out | growth extends the flat runway |
| No growth | 11 months | 10.6 months flat |
| Already profitable | profitable — no runway limit | no runway limit |
FAQFrequently asked questions
What is the difference between gross and net burn?
Gross burn is total monthly spend. Net burn subtracts revenue, and is what actually drains the bank account.
How do I calculate runway?
Cash divided by net burn. This page also projects it month by month with growth applied, which is usually more realistic.
When should I start raizing?
With at least six months left. A raize takes three to six months, and negotiating on a short runway costs you the terms.
What is a burn multiple?
Net burn divided by net new revenue — how much you spend to add a unit of revenue. Under 1.5 is generally considered efficient.
Does growth always extend runway?
Only if revenue grows faster than expenses. If costs grow at the same rate, growth changes nothing.
Where these figures come from
- Reichheld (2003), Harvard Business Review — The One Number You Need to Grow — the paper that introduced Net Promoter Score
- US Securities and Exchange Commission — the US securities regulator
Last checked: September 2026. These are the industry-standard definitions; where companies commonly disagree, the page says so.