Calculate Runway in Months From Cash and Burn

Excel & Google Sheets

How it works

Runway is cash divided by net monthly burn — the amount by which expenses exceed revenue each month. $240,000 in the bank burning $20,000 a month is 240000/20000 = 12 months of runway. Use net burn (spend minus income), not gross spend, or you'll understate your runway. And handle the good problem: a break-even or profitable month has zero or negative burn, which makes the division return #DIV/0! or a meaningless negative. Guard it with =IF(B2<=0,"Profitable",A2/B2) so the model reads correctly in every scenario.

A2

Cash on hand — the current bank balance.

/B2

Divided by net monthly burn: monthly expenses minus monthly revenue.

IF(B2<=0,"Profitable",…)

The guard: zero or negative burn means you aren't burning — no runway math applies.

When to use it

Use it in board decks and fundraising models, monthly finance reviews, and hiring plans — anywhere "when do we run out of money at this pace?" drives the decision.

Common mistakes

• ✕Dividing by gross spend instead of net burn.

  ✓If you spend 50k but collect 30k, burn is 20k. Using 50k cuts the runway figure by more than half and triggers false alarms. Burn = expenses − revenue.

• ✕#DIV/0! or negative months when burn hits zero.

  ✓A break-even month makes the plain division fail. Use =IF(B2<=0,"Profitable",A2/B2) so the model stays readable.

• ✕Using one lucky month's burn.

  ✓Burn is lumpy — an annual insurance bill or a big invoice skews any single month. Average the last 3 months: =A2/AVERAGE(B2:B4).