Divide the cash balance by net monthly burn to find the month funding runs out.
Flat-burn runway is a simple division, but burn almost always rises as headcount grows. Treating burn as a geometric series and solving for the number of months gives a materially shorter and more honest answer. Plans that assume flat burn overstate runway by months, and the shortfall lands exactly when a raise is hardest to complete.
Cash Runway
With burn growing g% a month, runway solves cash = burn × ((1+g)^n − 1) ÷ g for n
With burn growing g% a month, runway solves cash = burn × ((1+g)^n − 1) ÷ g for n Flat-burn runway is a simple division, but burn almost always rises as headcount grows. Treating burn as a geometric series and solving for the number of months gives a materially shorter and more honest answer.
Plans that assume flat burn overstate runway by months, and the shortfall lands exactly when a raise is hardest to complete.
This calculator takes 3 inputs: Cash available, Net monthly burn, Monthly growth in burn. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.