Runway is the number of months a business can continue operating at its current cash burn before running out of cash. It is calculated as cash on hand divided by net monthly cash burn (the amount cash decreases each month). Runway shrinks during loss-making months and extends when the business is cash-flow positive.
Runway is the most important single number for any business spending more cash than it generates — whether by design (a venture-backed startup investing ahead of revenue) or by accident (a profitable-on-paper business with bad cash timing). Runway answers the question "how long do I have before I have to do something different?" — raise capital, cut costs, accelerate collections, or shut down. Runway is calculated on net cash burn, not gross expenses, because revenue partially offsets spending. A business losing $40K of cash per month with $400K in the bank has 10 months of runway. If burn drops to $20K, runway doubles to 20 months — small burn improvements compound into significant time.
Runway (months) = Current Cash Balance ÷ Net Monthly Cash Burn where Net Monthly Cash Burn = Monthly Cash Outflows − Monthly Cash Inflows
Runway converts the cash balance into time — and time is what owners actually plan against. "$280K in the bank" is a number; "7 months of runway" is a decision frame. When runway drops below 6 months, every decision changes — hiring slows, marketing tightens, the conversation with the bank or investor starts. Owners who watch runway weekly avoid the most common failure mode in small business: discovering the bank balance is dangerously low only after a big customer pays late or a tax bill arrives. Even profitable businesses should know their runway as a stress-test metric in case a major customer churned or revenue stalled.
Fynso calculates runway every day using your live bank balances, AR, AP, and recurring obligations. The daily brief surfaces runway alongside the trend — "runway 9.2 months, down from 11.4 last month, driven by an AR slowdown from your top three customers." When runway crosses key thresholds (12, 9, 6, 3 months), Fynso flags it before it becomes a crisis. Scenario tools let owners ask "what does runway look like if I hire two engineers?" or "what if I cut marketing by 30%?" — turning runway into a decision lever, not a passive measurement.
Early-stage SaaS
A pre-revenue SaaS with $600K raised and burning $50K/month has 12 months of runway. The team plans the next fundraise for month 6 — leaving 6 months of buffer in case the raise takes longer than expected. Running a fundraise with under 4 months of runway dramatically weakens negotiating position.
Service business in transition
An agency that has been profitable for years takes on a major hire and a new office lease, pushing burn to $25K/month while pipeline catches up. With $300K of cash, runway is 12 months — comfortable but not infinite. The owner sets a runway floor of 6 months and commits to a hiring freeze if it's hit.
Restaurant during slow season
A seasonal restaurant generates 60% of annual revenue in Q3 and runs negative cash flow in Q1 and Q4. With $180K of cash entering the slow season and $30K/month negative cash flow, runway through the slow months is 6 — which is exactly enough to hit the busy season without a credit line.
Get product updates and access to Fynso features built for appointment-based operators.