How many months of runway if revenue drops by 25%?
Not the worst case, but a realistic bad case. Losing a quarter of your revenue is the kind of thing that happens when a big client downsizes, a seasonal dip is worse than expected, or a market shift hits your pipeline. Here is how to model it.
The short answer
How long would your cash last at 75% revenue? Take your monthly expenses, subtract 75% of your monthly revenue, and the difference is your net monthly cash burn under this scenario. Divide your current cash by that burn rate. That is your runway at 25% reduced revenue.
Why a 25% revenue drop is the most useful stress test
Zero revenue is dramatic but unlikely for most businesses. A 25% dip is the scenario that actually happens. Your second-largest client cuts their contract in half. A seasonal slowdown lasts two months longer than expected. A new competitor takes some of your pipeline.
The 25% test answers a practical question: if business gets meaningfully worse but does not collapse, how long can you hold on? That answer determines whether a bad quarter is a temporary setback or a spiral into crisis.
A business with 8 months of runway at 25% reduced revenue has room to adapt. A business with 2 months does not. Knowing the difference changes how aggressively you pursue new business, how carefully you manage expenses, and whether you need a line of credit before you need it.
How the 25% revenue drop scenario works
This calculation is slightly more involved than basic runway because you still have some revenue coming in. Here is the math:
If your expenses already exceed 75% of your revenue (meaning your margins are under 25%), this scenario puts you in a loss position immediately. The runway clock starts ticking as soon as the revenue drops.
How to model a 25% revenue decline in QuickBooks Online
You need numbers from two reports, then a simple spreadsheet calculation.
- 1Get your monthly revenue and expenses
Go to Reports→ “Profit and Loss.” Set the date range to the last 3 months. Note Total Income and Total Expenses. Divide each by 3 for your monthly average.
- 2Get your cash balance
Go to Reports→ “Balance Sheet.” Set the date to today. Note “Total Bank Accounts” under Current Assets.
- 3Run the scenario math
Multiply your average monthly revenue by 0.75. Subtract that from your average monthly expenses. That gap is your net monthly cash burn under this scenario. Divide your cash by that number.
- 4Consider what you could cut
Look at your P&L expense categories. If revenue dropped 25%, which expenses could you reduce? Ad spend, contractors, and discretionary costs are usually first. Payroll and rent are harder to cut. Factor realistic cuts into your scenario for a more accurate picture.
Total time: about 15 minutes across two reports and a spreadsheet. The math is not hard, but the judgment calls (which expenses could you actually cut?) make this more of a strategic exercise than a reporting one.
How to model a 25% revenue decline in Xero
Same calculation, Xero reports.
- 1Pull revenue and expenses
Go to Accounting → Reports→ “Profit and Loss.” Set the period to the last 3 months. Note Total Revenue and Total Operating Expenses. Divide by 3 for monthly averages.
- 2Get your cash position
Go to Accounting → Reports→ “Balance Sheet.” Find “Bank” under Current Assets.
- 3Calculate adjusted runway
Revenue x 0.75, then subtract from expenses to get net burn. Cash / net burn = months of runway. Xero's comparison view helps you see expense patterns, but you still need a spreadsheet for the scenario math.
Total time: about 15 minutes. Xero does not have built-in scenario modeling, so the stress test calculation happens in a spreadsheet.
Why stress testing needs to happen regularly, not once
Running this calculation once is useful. Running it monthly is what actually protects you.
- Your inputs change every month. Revenue shifts, expenses creep, cash fluctuates. A scenario that showed 7 months of runway in January might show 4 months by April if margins have been shrinking.
- Combining reports and doing math takes discipline. You need to pull the P&L, pull the Balance Sheet, open a spreadsheet, and run the scenario. That is 15 minutes you will almost certainly skip in a busy month.
- The trend matters more than any single number. Is your 25% scenario getting better or worse? You need several months of data to see the trajectory.
Or get stress test results automatically, every month
Bottomline runs the 25% revenue decline scenario automatically every month as part of your survival analysis. It uses your actual revenue, expenses, and cash position from your accounting software.
No spreadsheet. No manual math. Bottomline also shows you how this number has changed month over month, so you can see whether your buffer is growing or shrinking. If it crosses a threshold, your report flags it.