Biotech Cash Runway and Dilution: How Long the Money Lasts
Cash runway is how many months a company can keep going with the money it has. Take its cash and short-term investments and divide by what it spends each month. A biotech with less than a year of runway usually has to raise money soon, often by selling new shares, which dilutes existing shareholders.
How to calculate cash runway
The math fits on a napkin. Find the company's cash, cash equivalents and short-term investments in its latest quarterly report (the 10-Q). Then find how much cash it burned running the business in that quarter. Divide the quarterly burn by three to get a monthly number.
Runway in months = cash ÷ monthly burn.
A company with $200 million and a burn of $10 million a month has about 20 months. Companies often state their own runway in press releases ("cash runway into 2028"). That is useful, but check it against the numbers: plans can include money the company hopes to raise.
What dilution means for a biotech stock
When a biotech runs low on cash, it usually sells new shares. Existing shareholders now own a smaller slice of the company: that is dilution. It often happens through a public offering at a discount to the market price, or through an at-the-market (ATM) program that sells shares slowly into the market.
Dilution is not always bad. Raising money right after good data, at a high price, can fund a company for years. The painful kind is when a company has to raise money after bad news or at a low price, because it has no choice.
Biotech stocks trading below their cash
Sometimes the market values a biotech at less than the cash it holds. In plain terms, investors are saying the drugs are worth less than nothing, usually because they expect the company to burn the cash or fail.
Alto Neuroscience in June 2025 was one of these. Its market value was about $60 million, and it held about $160 million in cash, with roughly 29 months of runway and three hedge funds holding the stock. Six months later the stock had gone from $2.20 to $20.04, about 9x.
That is one example, not a rule. Across our 22,234 past stock-months, biotechs with more cash than market value and at least three funds holding rose 50% or more within six months about one time in three, against 13% for all biotechs. In 2024, a bad year for biotech, 46% of them fell 30% or more. Cheap can get cheaper.
Warning signs to look for
- Runway under 12 months. In our data, biotechs with high dilution risk or less than a year of runway fell 30% or more in six months 44.6% of the time, against 24.4% for all biotechs.
- A big catalyst after the money runs out. If the Phase 3 readout is 18 months away and the cash lasts 10, a raise is coming first.
- A new shelf registration or ATM program. It is the company getting ready to sell shares.
- A "going concern" warning in the 10-Q or 10-K. The auditors doubt the company can last a year.
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Frequently asked questions
Many investors look for at least 18 to 24 months, and enough cash to get past the company's next major catalyst. Under 12 months usually means a raise is close.
Dilution happens when a company issues new shares. Each existing share then represents a smaller part of the company, and if the new shares are sold at a discount, the price often falls.
New shares are usually sold below the market price, and more shares means each one owns less of the company. The drop is often worse when the raise comes after bad news or at a low price.
Its market value is lower than the cash it holds, so investors are putting a negative value on its drugs and business. It can be a bargain, or a sign the market expects the cash to be spent with little to show for it.
In its latest 10-Q or 10-K filed with the SEC: the balance sheet shows cash and investments, and the cash flow statement shows operating cash burn. Our company pages show cash, runway and dilution risk in one place.
Educational content only. Not financial advice. Past results don't predict future ones.