How to model cash runway
Runway is not a single number in a pitch deck - it is a moving target that changes with hiring, revenue, and payment timing. Here is how to model it properly.
Why a single runway number lies
Dividing cash balance by last month’s burn gives a headline number, but burn is rarely flat: a planned hiring wave, a seasonal revenue dip, or a large one-time expense can move real runway by months in either direction. A static number ages the moment a new hire signs.
Where teams get it wrong
- Using gross burn instead of net burn, ignoring real incoming revenue.
- Averaging burn over a period that includes an unusual one-time expense.
- Not updating the model when a hiring or spend decision is made.
- Modeling only one scenario, so a revenue miss is discovered on the bank balance, not the plan.
- Confusing cash runway with the separate question of when the next fundraise should start.
The Runway Modeling Framework
Five steps to a live runway model
- 1
Calculate net burn
Net burn equals total cash outflows minus total cash inflows over a representative recent period, not a single unusual month.
- 2
Establish the baseline runway
Divide current cash balance by net burn to get a starting-point number, then treat it as a baseline, not a forecast.
- 3
Layer in known changes
Add planned hires, committed spend increases, and expected revenue changes to project burn forward month by month.
- 4
Model at least two scenarios
Run the projection under a base case and a slower-revenue downside so runway is a range, not a point estimate.
- 5
Refresh monthly against actuals
Compare projected burn to actual burn every month and adjust the model - runway is only useful if it stays current.
How Fintra models runway for you
| Step | What Fintra does |
|---|---|
| Net burn | Cash-flow projection calculates net burn from real ledger cash in and cash out. |
| Baseline runway | Runway is computed live from current cash balance and trailing net burn. |
| Layer changes | Headcount planning and driver-based budgets feed planned hires and spend directly into the projection. |
| Scenario runway | Scenario planning runs runway under base and downside cases side by side. |
| Refresh monthly | Budget-vs-actuals flags when real burn diverges from the modeled projection. |
Cash runway
Runway (months) = Cash Balance / Net Monthly Burn
Net monthly burn is total cash outflows minus total cash inflows for a representative period - using gross burn instead overstates how fast cash is actually depleting.
Your runway modeling checklist
Set these up before your next board update
- Calculate net burn from a representative recent period, not a single month.
- Recompute baseline runway from the current cash balance monthly.
- Add every committed hire and spend increase to the projection.
- Build at least a base and downside runway scenario.
- Flag the runway date that would force a hiring freeze or spend cut.
- Compare projected to actual burn monthly and adjust the model.
- Separate the runway question from the fundraise-timing question explicitly.
Frequently asked questions
What is the correct formula for cash runway?
Runway in months equals current cash balance divided by net monthly burn, where net burn is total cash outflows minus total cash inflows. Using gross burn - ignoring incoming revenue - understates runway for any business with real income, so net burn is the number that matters for planning.
How often should I recalculate runway?
Monthly at minimum, and immediately after any material decision - a new hire, a large one-time expense, a customer win or loss. Runway calculated once and left unchanged ages quickly, because burn itself changes with headcount and revenue, not on a fixed schedule.
Should runway be one number or a range?
A range is more useful for decisions. A single baseline runway number is a reasonable headline, but modeling it under at least a base and a slower-revenue downside scenario shows how much cushion actually exists if things go worse than expected - which is the scenario that matters for hiring and spend decisions.
Does cash runway tell me when to raise money?
It is an input, not the answer. Most experienced operators start a fundraise process well before runway runs critically low - often when 6-9 months remain - because raising takes time and negotiating from a position of adequate cash produces better terms than negotiating from urgency.
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