Free calculator · Venture & Startup Finance
Venture Debt, Runway Extension & Its Cost
Calculates the runway extension venture debt buys, its share of the last equity round, and the total interest cost of carrying it. Inputs are the debt raised, the size of the last equity round, monthly net burn, the interest rate, and months outstanding.
By Devon Coombs, CPA, MBA · Teaching Professor of Finance, Santa Clara University · Reviewed August 2026
From the author: Devon Coombs, CPA, MBA teaches finance at Santa Clara University and works with corporate teams on practical AI.
AI training for finance teams · Consulting · The 10 Laws of Finance
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Venture Debt, Runway Extension & Its Cost
Runway extension
10.0 mo
debt ÷ monthly net burn
Total interest cost
$550K
debt × rate × yrs outstanding
Share of the round
31%
debt ÷ equity round
When growth holds, venture debt is cheap runway, a few percent of interest versus the equity a raise would cost. When growth misses, a breached covenant lets the lender accelerate and the same loan becomes a cliff. Stress-test the downside before signing.
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This calculator comes from the free Entrepreneurial Finance course, where the concept is taught with readings, worked examples, and practice questions.
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Built by Devon Coombs, CPA, MBA, Teaching Professor of Finance at Santa Clara University.