How Long Will My Cash Last? (Ecommerce Founder Guide)
If you run an ecommerce business and someone asked you: “Exactly how many months of cash runway do you have?” There’s a good chance you’d pause before answering.
Not because you’re careless — but because most founders don’t have a clear, up-to-date view of how long their cash will actually last. They have a sense of it. They don’t have a number they trust.
What “cash runway” actually means
Cash runway is simply: The number of months your business can continue operating before the bank balance hits zero. Not profit. Not revenue. Cash.
It answers one brutally practical question: If nothing changes, when do I run out of money? That might sound pessimistic — but it’s one of the most empowering numbers a founder can have.
Why most ecommerce founders misjudge runway
Runway is easy to misunderstand because ecommerce cash doesn’t move in straight lines. Founders usually miscalculate it for four reasons:
1. They assume revenue keeps growing
Most runway calculations quietly assume next month is better than this one. That works — until it doesn’t.
2. They ignore upcoming inventory payments
Large stock orders often sit just outside the forecast window. When they hit, runway collapses faster than expected.
3. VAT distorts reality
In the UK especially, VAT can make your bank balance look healthier than it really is — right up until the payment is due.
4. They average cash burn
Founders often divide current cash by “average monthly burn”. But ecommerce burn is lumpy:
Ad spend spikes
Inventory lands in chunks
Seasonality hits hard
Runway isn’t a straight line — it’s a series of cliffs.
Why growth often shortens runway
This is the part that catches people out.
As you grow, you often:
Spend more on ads before seeing returns
Order more inventory before it sells
Hire ahead of demand
On paper, the business looks healthier. In cash terms, the runway gets shorter.
This is why many ecommerce founders feel most stressed during growth, not decline.
What runway is actually for
Runway isn’t about panic. It’s about optionality.
A clear runway lets you:
Slow spend early instead of cutting late
Adjust pricing or ad strategy calmly
Delay hiring without guilt
Raise capital from a position of strength
Avoid forced decisions
Founders who see runway clearly make deliberate choices.
Founders who don’t often react too late.
Why spreadsheets struggle here
Many founders try to track runway in Excel or Google Sheets.
Early on, that works.
But as the business grows:
Assumptions multiply
Inputs change monthly
One missed update skews the entire picture
When founders stop trusting the model, they stop using it — and runway becomes a guess again.
Seeing runway clearly
You don’t need a perfect forecast to understand runway.
You need:
Cash as the central metric
Month-by-month visibility
The ability to change assumptions safely
This is part of a broader challenge around financial forecasting for ecommerce founders — especially once the business moves beyond simple spreadsheets.
If you want the full context, we explain this in detail in our main guide: Financial Forecasting for Ecommerce Founders (UK Guide)
Final thought
Most ecommerce businesses don’t fail suddenly. They run out of time.
Cash runway is how you see that coming: early enough to do something about it.
If you want to see your actual runway — not an estimate, not a guess — tools like FuturesAI are designed to make this visible in minutes, not days.
