Series B
A Series B is the second major institutional equity round a startup raises, typically occurring 18–30 months after Series A, after a company has proven its go-to-market model and needs capital to scale operations, expand sales teams, and enter new markets. The average amount raised in a Series B is approximately $27M, with a median post-money valuation of $117M.8 Startups on Carta raised a median Series B of $15.1M in Q3 2023, representing a 39.8% decline from the Q1 2021 peak, reflecting tighter market conditions.1
Structure and mechanics
A Series B is issued as preferred stock with the same structural features as a Series A — liquidation preferences, anti-dilution provisions, and board representation — but at a substantially higher valuation. As of Q1 2024, the median dilution in a Series B was 16.7%, down from 20.8% in Q1 2019.2 This decline reflects both the post-2021 funding contraction and a broader structural shift: well-performing companies have stronger negotiating leverage on price, allowing them to raise more capital while giving up less equity.
The median time between Series A and Series B is approximately 31 months, though this figure includes the extended gaps that became common after 2022.3 In 2020–2021, many companies raised Series B rounds within 12–18 months of their Series A as investors competed aggressively to deploy capital. Post-2022, as interest rates rose and exit activity declined, founders held off on raising to extend runway, and the interval lengthened. Bridge rounds — often at half the dilution of a primary round — became substantially more common, allowing companies to defer priced Series B negotiations until metrics improved.1
Lead investors at Series B are typically growth-stage specialists or multi-stage funds. Kleiner Perkins, General Catalyst, IVP, and Tiger Global have historically been active at the Series B. The lead investor conducts thorough financial diligence, builds a 5-year revenue model, and often brings in sector-specific operating partners to stress-test go-to-market assumptions. The process typically runs 6–12 weeks from first meetings to close.1
What investors require
Series B investors expect proof that the Series A thesis has been validated: the company has a repeatable, scalable go-to-market motion. In B2B SaaS, this means demonstrable GTM fit — the company can predictably acquire customers through a defined set of channels with improving unit economics. Andreessen Horowitz partner Constanza Diaz has described the distinction as: "Series A is about proving product-market fit and crafting your GTM strategy. At Series B you need to show GTM fit, so you can invest more heavily in the things that are already working."1
Quantitatively, Series B investors in 2024 look for 2x or greater year-over-year ARR growth, net revenue retention above 110%, and a burn multiple (net burn divided by net new ARR) below 1.5x. A company with $5–10M ARR growing 150% year-over-year with a clear sales funnel and healthy CAC payback periods (under 18 months) is the median Series B candidate.4 Companies with a low burn multiple and a credible path to break-even within 12 months rank higher in the current environment than those projecting rapid growth with no profitability line.
The market correction that began in early 2022 shifted investor preferences sharply away from growth-at-all-costs and toward capital efficiency. Founders who raised a Series A at elevated 2021 valuations and then needed to raise a Series B in 2022–2023 found themselves with limited options: flat rounds, down rounds, or extensions.2 Down rounds — those at a valuation below the prior round — hit their highest rate since 2018 in 2023, according to Carta data, particularly for companies that had grown headcount aggressively on their Series A runway without achieving proportional ARR growth.1
Notable examples
Airbnb raised a $112M Series B in 2011 led by Andreessen Horowitz with co-investors including General Catalyst, Jeff Bezos, and Digital Sky Technologies.5 The round came six months after Airbnb's $7.2M Series A and reflected the company's rapid international expansion. By the time of the Series B, Airbnb had expanded to 89 countries and was processing bookings at a pace that made the $112M valuation step-up from the Series A uncontroversial.
Slack raised a $120M round in October 2014 led by Kleiner Perkins Caufield & Byers and Google Ventures, at a $1.12 billion valuation — making it a unicorn on its first major post-launch financing.6 The company had launched publicly in February 2014 and reached 73,000 daily active users within 24 hours. Within the first year of operation, Slack was processing over $1M in daily contract value, which anchored the investors' willingness to price the round above $1B.
Dropbox raised a $250M Series B in 2011 with investors including Index Ventures, Benchmark, Goldman Sachs, Greylock Partners, Sequoia Capital, and Accel Partners.5 The Dropbox Series B was one of the largest ever raised to that point by a consumer software company and reflected the firm's then 50 million registered users and $240M in annual revenue run rate. Zynga raised a $300M Series B in 2010 — the largest Series B in technology history at the time — led by Kleiner Perkins, Andreessen Horowitz, and Tiger Global.5
Market context
Total venture capital deployed into Series B deals in the United States declined sharply from 2022 to 2023 as general partners slowed new commitments in response to poor exit activity. The Q4 2024 NVCA report noted that 70% of exits in 2024 involved companies that had not raised beyond Series A, indicating that most Series B-backed companies were either staying private longer or experiencing acquisition outcomes that did not generate headline-level returns.7 The time between rounds for all series hit decade highs in 2024.
Lyft's $60M Series B in May 2013, led by Andreessen Horowitz, illustrates how market expectations for Series B candidates changed between eras.5 Lyft had launched in June 2012 and reached 30 cities within a year before raising; the round was predicated on operational expansion rather than already-proven unit economics. In the 2023–2025 environment, equivalent companies are expected to show CAC payback and operational leverage before a Series B closes, rather than projecting those improvements as post-investment targets.