Cash Flow Runway & Resilience Calculator
Two numbers every Irish business owner should know. How many months of runway you have at your current burn rate, and how long your cash would last if revenue stopped tomorrow. Enter four figures and get both, with a resilience rating.
Indicative planning tool, not financial advice. Best revisited whenever your numbers change.
Runway (current trajectory)
6.7 months
You are burning €3,000 per month. Your cash alone lasts 6.7 months.
Cash runs out around December 2026.
Resilience (if revenue stopped)
1.3 monthsCritical
If revenue stopped tomorrow, your cash reserve would cover about 1.3 months of operating costs.
What your critical rating means
Under 3 months of cover. This is the danger zone. Prioritise collecting receivables, deferring non-essential spend, and lining up a facility before you need it.
How the numbers work
- Net monthly cash flow = revenue minus costs. A negative figure is your monthly burn.
- Runway = (cash + available credit) divided by monthly burn. Shown only when you are spending more than you earn.
- Resilience = cash divided by monthly costs - months you could survive with zero income. Credit is deliberately excluded here.
- Resilience bands use the widely cited 3-6 month operating-reserve guideline. They are editorial best-practice, not a regulatory standard.
- This is a simple steady-state model. It does not account for seasonality, one-off costs, tax payment dates, or changing run-rates.
Runway and resilience are two different questions
Most cash calculators answer only one question: at my current burn, when do I run out? That is your runway, and it matters most for businesses that are investing ahead of revenue. But a profitable business has effectively unlimited runway and can still be dangerously exposed - if its biggest client leaves or a payment is delayed, how long could it actually survive on the cash in the bank? That is resilience, and it is the question this tool puts front and centre.
We measure resilience as the number of months your cash reserve would cover your operating costs if revenue dropped to zero tomorrow. It is a deliberately harsh test, because the moments that kill businesses - a lost contract, a bad debt, a sudden shock - tend to hit revenue and access to credit at the same time.
How to read your resilience rating
- Critical (under 3 months): the danger zone. Focus on collecting what you are owed, deferring non-essential spend, and arranging a facility before you need it.
- Fragile (3 to 6 months): workable but thin. One late payment or lost client could squeeze you. Build toward six months.
- Stable (6 to 12 months): a healthy buffer for most Irish SMEs. Enough to weather a bad quarter or fund a measured investment.
- Resilient (over 12 months): strong. Consider whether some reserve could be put to work while keeping a comfortable buffer.
Get the inputs right
The result is only as good as the figures you feed it. Use cash actually collected, not invoiced, for revenue - a healthy order book is not the same as money in the bank. Include every cash outflow in costs: payroll, rent, software subscriptions, loan repayments, owner drawings, and crucially the VAT and PAYE you owe Revenue. That tax money sits in your account until the filing date but it is not yours to spend, and treating it as a buffer is one of the most common ways Irish SMEs get caught short.
Why revisit this regularly
Runway and resilience move every month as your cash, revenue, and costs change. Bookmark your result - the share link saves your inputs - and re-run it at month-end or whenever something material shifts: a new hire, a price change, a big invoice in or out. Watching the trend matters more than any single snapshot.
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What to look for
- Use cash actually collected, not invoiced, when estimating monthly revenue.
- Always set aside VAT and PAYE - that money is not yours to spend.
- Aim for at least three to six months of operating costs in reserve.
- Re-run the numbers monthly and watch the trend, not just the snapshot.
Common mistakes to avoid
- Counting your order book as if it were cash in the bank.
- Treating VAT and PAYE balances as a spending buffer.
- Relying on an overdraft that can be pulled when you most need it.
- Only checking cash flow when something has already gone wrong.
Frequently asked questions
What is cash flow runway?
Runway is how many months your business can keep operating before it runs out of cash, at your current rate of spending more than you earn. It is calculated as your cash on hand (plus any available credit) divided by your monthly net burn.
What is the difference between runway and resilience?
Runway measures your current trajectory - how long until the cash runs out at the current burn rate. Resilience is a stress test - how many months of operating costs your cash reserve could cover if revenue stopped entirely tomorrow. A profitable business has unlimited runway but can still have weak resilience.
How many months of cash reserve should an Irish SME hold?
A widely cited guideline is three to six months of operating costs. Under three months is considered fragile to critical; six to twelve months is healthy for most SMEs. The right figure depends on how predictable your revenue is and how quickly you can cut costs.
Should I include VAT and PAYE in my monthly costs?
Yes. Money you owe Revenue for VAT and PAYE is not yours to spend, even though it sits in your account until the filing date. Including those set-asides in your monthly costs gives a more honest picture of your real runway and resilience.
Does available credit count toward resilience?
It extends your runway, so the calculator adds it there. But it deliberately excludes credit from your resilience score, because an overdraft or facility can be reduced or withdrawn in exactly the conditions where you would need it most. Resilience is measured on cash you actually hold.
Related resources
- Accounting software for Irish businesses - real-time cash flow dashboards and forecasting built in.
- Invoicing software for Ireland - get paid faster with automated reminders and online payment.
- Business banking in Ireland - accounts, overdrafts, and the credit facilities that extend your runway.
- VAT Registration Threshold Checker - see whether your turnover means you must register for VAT.
- Find My Stack - AI-powered software stack recommender for Irish SMEs.
Results are indicative only and based on the information provided. Data may not reflect current vendor offerings and is subject to change. Always verify details directly with vendors before making purchasing decisions.