Runway calculator
Runway is cash divided by net burn — what you spend each month minus what you earn. With revenue growing, the simple division understates it, because each month’s burn is smaller than the last.
The working
Every row computed from your inputs.
| Revenue | Costs | Net | Cash left | |
|---|---|---|---|---|
| Month 1 | €4,000 | €22,000 | -€18,000 | €222,000 |
| Month 2 | €4,480 | €22,000 | -€17,520 | €204,480 |
| Month 3 | €5,018 | €22,000 | -€16,982 | €187,498 |
| Month 4 | €5,620 | €22,000 | -€16,380 | €171,117 |
| Month 5 | €6,294 | €22,000 | -€15,706 | €155,411 |
| Month 6 | €7,049 | €22,000 | -€14,951 | €140,461 |
| Month 12 | €13,914 | €22,000 | -€8,086 | €72,533 |
Runway, step by step
Net burn, not gross spend, is the figure that matters. A company spending 60,000 a month with 20,000 of revenue burns 40,000, and the runway calculation that ignores revenue is wrong by a third. Month-by-month modelling matters once revenue is growing at any real rate: constant-burn arithmetic can understate runway by several months, which is the difference between raising now and raising from strength.
The useful output is not the single number but the date. "Fourteen months" becomes a decision when you write it as a month in the calendar and put the fundraise, which takes three to six months, in front of it.
Where this number misleads you
Runway assumes the plan happens. It does not know about the hire starting in March, the annual insurance renewal, or the enterprise customer paying 90 days late. Model the lumpy outgoings explicitly, and treat anything beyond six months as a scenario rather than a forecast.
Questions people ask
How do I calculate runway?
Divide cash in the bank by net monthly burn, where net burn is monthly spend minus monthly revenue. If revenue is growing, model it month by month instead: subtract each month’s net burn from the balance until the balance reaches zero, which gives a later and more accurate date.
What is the difference between gross and net burn?
Gross burn is everything you spend in a month. Net burn is that minus revenue received. Runway is calculated on net burn. Investors usually ask for both, because gross burn shows the size of the operation and net burn shows how fast the clock is running.
How much runway should a startup have?
The common rule is 18 to 24 months after a raise, and never fewer than 12 when you start fundraising — a round takes three to six months to close, and negotiating with under six months of cash left is negotiating from a position everybody in the room can see.