What Is Runway?

Runway tells founders and finance teams the most existential number in the business: how long until the money runs out. It sets the clock for either achieving profitability or raising additional funding, and influences virtually every strategic decision in a pre-profit company.

The basic formula is: Runway (months) = Cash Balance / Monthly Net Burn Rate. However, sophisticated FP&A teams model runway dynamically, incorporating expected revenue growth (which reduces net burn over time) and planned spending changes.

Best practice for UK startups is to maintain a minimum of 12-18 months of runway. Starting fundraising with less than 6 months of runway creates negotiation pressure that typically leads to worse deal terms. The fundraising process itself typically takes 3-6 months, so a company with 6 months of runway when starting to raise may be dangerously close to running out.

FP&A teams can extend runway through several strategies: reducing non-essential spending, negotiating extended payment terms with suppliers, accelerating customer collections, claiming R&D tax credits (which provide cash refunds for loss-making SMEs), applying for HMRC time-to-pay arrangements, and accessing government grant funding.

Runway modelling should include scenario analysis: base case (current trajectory), upside case (faster revenue growth or successful fundraise), and downside case (revenue shortfall or unexpected costs). The downside scenario determines the true risk profile.