Series B
Also known as Series B Round, Series B Financing
Series B is the scaling round that funds go-to-market expansion and team build after a company has proven its initial GTM motion. The round shifts the question from 'does this work?' to 'how big can this get?'
In depth
Series B is the awkward middle stage of venture. The company has cleared most of the existential risk, the burn is real, and the question shifts from "does this work?" to "how big can this get?" Series B leads are typically growth-stage funds writing checks substantially larger than the Series A, sometimes with a tranche structure tied to forward milestones.
Series B sits in a strange position on the dilution curve. Round sizes grow, but valuations often grow faster, so the percentage of the company sold per round tends to compress relative to Series A. The mechanic is straightforward: investors are paying for a known company at a higher absolute valuation, not for risk underwriting on an unproven model.
The capital structure also gets more complex. Pay-to-play provisions, ratchets, and aggressive participating preferred terms reappear in tougher market conditions, and the share of rounds with structured terms is a useful proxy for how tight the market is.
Why it matters
Series B is where venture math starts to mean something for LPs. The company is no longer a binary, and the markup from B to C is one of the cleaner predictors of fund-level TVPI in growth-oriented portfolios. A Series A check that marks up to a clean Series B at 2-3x cost typically tracks to a meaningful exit multiple on average, though the variance around that mean is wide.
For founders, Series B is also the first stage where secondary sales become feasible. Lead investors often allow a small share of the round to clear early shareholder positions, releasing pressure on founders who have been paying themselves below market for years.
Worked example
A B2B SaaS company raises a $30M Series B at $170M pre-money, $200M post-money. The lead does not require a pool top-up because the existing pool is sufficient.
Series B dilution: $30M / $200M = 15.0%
No pool top-up this round.
Founder ownership before: 45% (post-Series A)
Founder ownership after: 45% × (1 - 0.15) = 38.25%
Founders exit Series B with roughly 38% on a fully diluted basis. The Series B lead holds 15%, with the remainder distributed across Series A investors, the pool, and seed-stage holders who have not fully cleared their pro rata.
Frequently asked
What milestones do I need to raise a Series B?
Typical Series B companies show meaningful ARR, strong net retention, a working sales motion, and a credible path to several multiples of current revenue. The round funds scaling that motion, not finding it. Investors expect at least a couple of quarters of consistent growth at scale, not a single big quarter.
How big is a Series B?
Round sizes vary by sector and geography, typically much larger than a Series A and funding 18-24 months of accelerated growth. Bridge Series B rounds (companies extending into a Series B without true scale) can clear at headline valuations but usually with worse terms — tighter milestones, structured preferences, or tranching.
How much dilution at Series B?
Series B dilution typically lands around 12-18%, often lower than Series A as round sizes grow without proportional valuation increases. Founders usually exit Series B holding roughly 25-35% on a fully diluted basis, depending on what came before.
Series A vs Series B: how is it different?
Series A funds the search for repeatable GTM; Series B funds scaling it. Series B leads are usually growth-stage funds, not the early-stage firms that led the A. The round often introduces a second board observer, more aggressive milestone-tied tranches, and the first real conversations about secondary sales for early shareholders.
What if I can't raise a Series B?
The fallback is an extension round, a bridge convertible, or a recapitalization. Companies that stall on the path to Series B often pivot to capital efficiency and run for cash flow rather than chase the next priced round. The Series A-to-B gap has stretched in recent years, so a slow path is not automatically a failed path.