Cash planning
How to Calculate Cash Runway
Cash runway estimates how many months a current cash balance can support a positive net burn. It is a planning horizon, not an expiration date: the calculation assumes cash movement continues at the modeled pace and must be updated as reality changes.
What cash runway means
Cash runway is the estimated time until available cash reaches zero if net burn remains constant. A company with $360,000 of available cash and $45,000 of monthly net burn has eight months of runway under that simple model.
Available cash should reflect the balance actually usable for operations. Restricted funds, customer deposits held for a specific purpose, or minimum reserves may need to be excluded. Net burn is cash outflow minus cash inflow per month, calculated on a compatible basis.
Runway helps put hiring, pricing, fundraising, collections, and cost changes on a timeline. It does not know when a large annual bill is due, whether sales are seasonal, or whether a future contract will close. A month-by-month cash forecast remains essential.
The formula and each variable
Cash runway in months = Available cash balance ÷ Monthly net burn
- Available cash balance
- Cash that can actually fund operations after restrictions or intentional reserves.
- Monthly net burn
- Average monthly cash outflow minus average monthly cash inflow, when the result is positive.
- Months
- A modeled duration at an unchanged rate, not a guaranteed deadline.
When net burn is zero or negative, division does not produce a meaningful finite operating runway. Report cash-neutral or net cash generation instead.
How to calculate it step by step
Determine usable cash
Start from verified balances and subtract funds that are restricted, committed, or intentionally held outside the operating plan.
Measure net burn
Use actual operating cash outflow minus operating cash inflow over a representative period, expressed per month.
Check the sign
Continue with division only if net burn is positive. Zero is cash-neutral; a negative result is net cash generation.
Divide cash by burn
Keep reasonable precision for planning, then translate the result to an approximate date with appropriate caution.
Build a forward schedule
Layer in payroll dates, taxes, annual contracts, receivables, hiring, seasonality, and downside cases.
Worked example
Worked example: a product design studio
The studio has $280,000 in available cash. Average monthly cash outflow is $92,000, while collected client payments average $52,000. The current plan therefore consumes $40,000 per month.
- Available cash
- $280,000
- Monthly cash outflow
- $92,000
- Monthly cash inflow
- $52,000
- Monthly net burn
- $40,000
- Net burn = $92,000 − $52,000 = $40,000 per month.
- Cash runway = $280,000 ÷ $40,000 = 7 months.
- At an unchanged average, modeled cash falls by about $40,000 each month until the seventh month uses the remaining balance.
Seven months is a decision window, not seven months of guaranteed safety. If clients pay late or a tax payment falls early, the minimum cash point can arrive sooner. If collections improve or spending falls, runway extends.
Positive burn, cash-neutral, and net generation
A positive net burn supports the ordinary runway formula. If the studio’s inflow rose to $92,000, net burn would be zero: current operating inflow matches outflow. The business is cash-neutral under those assumptions, so there is no finite depletion date to report.
If inflow rose to $100,000 while outflow stayed $92,000, the operation would generate $8,000 per month. Displaying infinity as an ordinary numeric runway would imply certainty that the cash-generating state lasts forever. Say “net cash generation” and model future scenarios instead.
The zero-cash scenario
When available cash is zero and net burn is positive, runway is zero months. The business already lacks an operating cash buffer under the model. A formula should not hide that condition behind a blank result.
When both cash and net burn are zero, division is still not meaningful. The company is cash-neutral in the narrow operating model but has no cash cushion for timing differences or unexpected obligations.
A runway date is only as stable as the forecast
Converting seven months into a date can make the estimate feel more exact than it is. Cash does not usually decline in a straight line: payroll clusters, clients pay unpredictably, and annual charges create steps.
Use the simple date for communication, then maintain a weekly or monthly cash schedule. Set internal action dates before the modeled end so financing, cost changes, or revenue work have time to take effect.
Small burn changes can move the horizon
At $40,000 net burn, $280,000 lasts seven months. At $50,000, it lasts 5.6 months. At $30,000, it lasts about 9.3 months. This sensitivity makes burn assumptions more important than extra decimal places.
Build a base case, a downside case with slower collections or higher costs, and a plan case tied to specific actions. Do not count unsigned revenue or unapproved financing as available cash.
What changes runway
Can extend runway
- Faster collections or more recurring operating inflow.
- Lower net burn through deliberate cost or timing changes.
- New unrestricted cash that is actually available.
- Staged commitments tied to validated milestones.
Can shorten runway
- Customer delays, churn, refunds, or seasonal revenue weakness.
- Hiring and vendor commitments before inflow grows.
- Restricted or committed cash treated as freely available.
- Large payments omitted from a smooth monthly average.
Common mistakes
Where the calculation goes wrong
Dividing by gross burn
Gross outflow ignores operating inflow and understates runway. Use positive net burn for the ordinary formula.
Counting restricted cash
Funds that cannot cover general operations should not create apparent operating runway.
Showing infinity for zero burn
Cash-neutral conditions may change. Describe the state rather than presenting an unlimited numeric forecast.
Waiting until the modeled end date
Financing and operational changes require lead time. Set decision triggers well before cash is exhausted.
Action checklist
Before you use the result
- Verify balances and define available operating cash.
- Exclude restricted funds and document reserves.
- Calculate monthly net burn from compatible cash data.
- Classify the result as positive burn, cash-neutral, or net generation.
- Use division only for a positive net burn.
- Model uneven payments and at least one downside case.
- Set action dates before the estimated runway ends.
FAQ
Questions beyond the basic calculation
Should a credit line count as cash runway?
An undrawn credit line is not cash and may have conditions. You can model it as a separate financing scenario, but keep current available cash runway visible.
How often should runway be updated?
Update whenever cash, burn, or the operating plan changes materially. Businesses with short runway or volatile collections may review it weekly; others may use a monthly cadence.
Can runway increase without raising money?
Yes. Higher cash inflow, lower outflow, improved collections, or delayed optional commitments can reduce net burn and extend the modeled horizon.
Is a long runway proof that the business is healthy?
No. A large cash balance can create long runway even when unit economics or demand are weak. Review profitability, growth quality, and strategic progress alongside cash duration.
Note: This guide is for general cash-planning education and is not financial, investment, accounting, tax, or legal advice. Use complete records and qualified advice for material decisions.