Series A vs Series B and how long the cash must last

What is the difference between Series A and Series B?

A Series A and a Series B are two priced rounds in venture deals sold in order, and the letter records only the order of the round: Cooley’s second-quarter 2026 report put the median Series B pre-money valuation at $185.2 million, while Crunchbase News’s May 2026 analysis put the median US Series A round at $15 million in 2025. One is a valuation and the other a round size, from different datasets, so they are not a ratio.

Martin Casado, a general partner at Andreessen Horowitz, wrote in September 2018 that seed, A, B and C are a bad approximation of a company’s stage, and that his firm uses team, product, repeatable sale and unit economics instead. The table sets out what the published sources say about each round.

	Series A	Series B
What the investor mainly tests	Whether customers want the product: CRV says a competitive B2B SaaS raise generally starts at $2 million to $5 million of annual recurring revenue	Whether the sale repeats at a cost that scales (Unmatched Capital’s reading of a16z’s stages)
Round size, US	Median $15 million in 2025, quartiles $7 million and $25 million (Crunchbase)	In 2026 so far, less than a third of rounds under $30 million, and at least 110 companies raising $100 million or more (Crunchbase, rounds of $1 million or more)
Valuation	Median pre-money fell in Q2 2026; the report text gives no figure (Cooley)	Median pre-money $185.2 million in Q2 2026 (Cooley)
Lead investor’s stake	A lead generally wants 20% (Y Combinator, 2019)	No published figure found
Median wait to the next round	28 months to a Series B (Crunchbase, 2024)	No published figure found

The samples differ. Cooley’s is the 166 venture financings it reported handling in the quarter, and Crunchbase’s is the rounds announced in its database. Neither is a census: the Crunchbase figures above cover US rounds, and the Cooley report page gives no geographic split. The stage before, seed, is covered in pre-seed vs seed.

How big are Series A and Series B rounds in the US, and what are they valued at?

A US Series A round in 2025 had a median size of $15 million, with a lower quartile of $7 million and an upper quartile of $25 million, according to Crunchbase News’s May 2026 analysis of its own data. Series B rounds are spread more widely. Crunchbase’s October 2026 analysis of US Series B rounds of $1 million or more found that less than a third of the deals in its sample were under $30 million so far in 2026, against about half between 2021 and 2025. At least 110 companies raised rounds of $100 million or more around the Series B stage, and there were just 26 rounds under $10 million. Investors put around $48 billion into financings around the Series B stage, and about two-thirds went to AI-focused startups.

Valuation figures from law firms are narrower. Cooley handled 166 reported venture financings in the second quarter of 2026, and its report puts the median Series B pre-money valuation at $185.2 million, up from $152.5 million in the first quarter. That first-quarter figure is not the one Cooley printed three months earlier: its first-quarter report said the Series B median had fallen to $165 million. Neither report explains the change, and the second-quarter report restates another first-quarter figure as well (pay-to-play provisions, from 7.3% to 7%), so a figure in one quarterly report may be revised in the next. The second-quarter report says the median pre-money valuation decreased for Series A without giving a dollar figure in its text, and no Series A valuation median is given here to put beside it.

Round outcomes help to read those medians. In the second quarter of 2026, up rounds were 83.6% of the deals Cooley handled, flat rounds 4.3% and down rounds 12.1%, across all stages. Cooley said the Series B pre-money rise was the largest of any stage.

Crunchbase’s Series B sample and Cooley’s are different populations, and neither counts every US Series B. A founder pricing a round can use both as the middle of the deals each publisher saw, which is a reference point for a negotiation and no quote for any one company.

How do Series A and Series B rounds compare in Europe and the UK?

European Series A rounds are smaller than American ones in Crunchbase’s and Atomico’s data, and the gap narrows at Series B. In Crunchbase News’s February 2022 analysis of 2021 rounds, the median Series A in Europe was $8.5 million against $13 million in the US, and the median Series B was $29.4 million against $33 million. The average Series B was $47.3 million in Europe and $50.2 million in the US. That is data from 2021, and it is the most recent median comparison of the two regions found.

More recent figures are averages from Atomico’s State of European Tech report. TechCrunch reported in November 2024 that the average European Series A was $10.6 million, up from $9.3 million in 2023, and the average Series B $25.4 million, up from $21.3 million. TechCrunch added that the US continues to outpace Europe on round sizes overall. An average and a median are different measures, and a 2021 median and a 2024 average are not comparable, so the three-year sequence cannot be read as growth or decline.

Crunchbase does not separate Series A from Series B in its European quarterly reports. It counts both as early-stage, together with other round types: early-stage funding was $5.3 billion across more than 240 rounds in the first quarter of 2026, and $8.6 billion across 250-plus startups in the second quarter. Late-stage funding, Series C and later, was $9.2 billion across 83 deals in the first quarter and $12.1 billion in the second, up 90% year on year. The UK raised $10.4 billion in the second quarter of 2026, its third-largest quarter on record, widening its lead over other European countries, according to the same report, but that figure covers every stage.

A UK investor in either round may be able to claim tax relief. HMRC’s guidance, updated on 6 April 2026, gives 30% Income Tax relief under the Enterprise Investment Scheme on up to £1 million a year, or up to £2 million if at least £1 million goes into knowledge-intensive companies. Whether a particular round qualifies depends on conditions on the company side that are not covered here.

Atomico, in the same TechCrunch report, put European startup valuations on average 29% to 52% below American ones, without a split by series. No current figure for UK or European valuations by series, or for European terms by stage, was found, so the terms data below are from US deals.

How long is it between Series A and Series B, and how many companies get there?

The median wait between a US Series A and a Series B was 28 months in 2024, and a minority of companies make the trip. Crunchbase News’s August 2024 analysis tracked over 4,400 US companies that raised a Series A in 2020 or 2021 and found that just over 1,600 had raised a Series B. That is roughly 36%, Unmatched Capital’s division of two rounded counts, and it is a floor, because Series Bs raised after August 2024 are not counted.

The 28-month median was, in Crunchbase’s words, by far the longest span since 2012, and the average hit a high of 31 months, tied with 2023. A gap can only be measured for companies that did raise the next round, so both figures describe survivors. The spread is wide: xAI closed the largest Series B of 2024 six months after its previous round, while Quantum Circuits raised its Series B six and a half years after its Series A.

Missing a B does not always mean failure, according to Crunchbase. Some companies shut down, but others were acquired, went public, took debt or extension rounds, or built a viable business without more equity.

The step before shows the same pattern. Crunchbase’s May 2026 analysis found that US companies that raised a seed of $1 million or more had a typical graduation rate of 55% or higher through 2020, but only 24% of the 2023 cohort and 16% of the 2024 cohort had progressed to later-stage funding or an exit. Younger cohorts have had less time, so those rates will rise, and the article puts the wait from seed to Series A at more than two years.

European companies have also been slower to reach a Series B. Atomico’s 2024 State of European Tech report, as reported by TechCrunch, found that just 16% raised a Series B within 15 months of the Series A in 2024. That is a share within a fixed window, not a median gap, so it cannot be set beside Crunchbase’s US figures.

How long should a Series A be planned to last?

A Series A plan should be tested against 31 months to the close of the Series B, the average gap for US companies in Crunchbase News’s 2024 analysis, and in Unmatched Capital’s analysis a plan shorter than that needs a reason. The same article says the average would have been higher had a few AI startups not raised so quickly, that the most common wait is two to three years, and that a wait beyond three and a half or four years is rare. Both the average and the 28-month median count only companies that raised a Series B, and just over a third of the 2020 and 2021 cohort had done so by August 2024. And the evidence a Series B investor tests, a sale that repeats, takes time to produce: Casado wrote that his firm talks to customers to diligence the duration of the sales cycle and the pipeline. A company outside the sectors raising fastest can test its plan against three years, the top of the range Crunchbase calls most common.

The gap runs from one round to the next, so it ends when the Series B closes, and the months spent raising the B fall inside it. It is time between rounds, not a measure of cash: Crunchbase does not say how the companies funded it, and it names debt and extension rounds among the routes companies took, so the Series A’s proceeds need not have paid for every month.

The counterargument is that fast outliers exist and that runway costs shares. xAI raised a Series B six months after its previous round, and a company that is growing quickly can raise again before 31 months pass. More cash at the Series A also dilutes more. In the hypothetical below, a $15 million round at a $60 million pre-money valuation gives the investor 20%; raising $16 million at the same pre-money valuation gives 21.05%, so the first extra $1 million costs existing holders about 1.05 percentage points, and each further million slightly less (0.93 points from $20 million to $21 million). If the post-money valuation stays at $75 million instead, it costs about 1.33 points (1 divided by 75). Both are Unmatched Capital’s calculations. A company that runs short anyway faces a bridge round.

The 36% floor does not shorten the plan. Any company in the 2020 and 2021 cohort that raises its B after August 2024 does so at least about 32 months after its Series A, longer than the 31-month average, so the companies still to convert are slower than the average, not faster. The 31 months describes Series B rounds in 2024, not this cohort, and the reasoning is Unmatched Capital’s from the cohort dates, not a Crunchbase figure.

What do investors check at Series A, and what changes at Series B?

Published investor checks are numeric for Series A and thin for Series B. CRV, a venture firm, wrote in March 2026 that a competitive Series A raise for a B2B SaaS company generally starts at $2 million to $5 million of annual recurring revenue (ARR), that 100% net revenue retention is the baseline and 110% to 120% is competitive, and that building a fundable business takes 12 to 18 months. A second CRV page, from July 2026, says that by Series A investors expect a burn multiple (net cash burned divided by net new ARR) below 2.0x, with the strongest companies operating closer to 1.0x. These are thresholds for B2B software. No published Series A or B thresholds for hardware, life sciences or other capital-intensive companies were read, and Crunchbase’s slowest example, Quantum Circuits, is a quantum computing company.

CRV publishes no Series B thresholds on those pages, and no venture firm’s numeric Series B checklist was found. The nearest primary description is Casado’s. For the repeatable sale, he wrote, Andreessen Horowitz talks to customers about the duration of the sales cycle and the pipeline, and for unit economics it pays special attention to ACV, customer acquisition cost and net dollar retention. He did not tie either stage to a Series B; the only Series B in the post is an example of a mismatched pitch, a company that claims to be raising a Series B to scale sales. Matching the two tests to a B is Unmatched Capital’s inference: a Series A investor mainly tests whether customers want the product, and a Series B investor tests whether the sale repeats at a cost that scales.

How do the terms change between Series A and Series B?

Cooley said liquidation preference structures remained favourable to companies in the deals it handled, which it does not split by series, and three terms can still change between A and B: who sits on the board, who is paid first and who may invest again. In the second quarter of 2026, Cooley reported that 95.8% of its deals had a 1x liquidation preference and 96.4% had nonparticipating preferred stock. In the second quarter, 8.4% had pay-to-play provisions, up from 7% in the first.

Y Combinator’s Jason Kwon, General Counsel at YC Continuity, wrote in 2019 that a clean Series A leaves the founders in control of the board, 2-1, and that a 2-2-1 board (two founders, two investors, one independent) is the way founders most often lose it at the Series A. The same page names the investor vetoes on a sale of the company and on a financing as the two most impactful vetoes, and lists a liquidation preference above 1x as a non-standard economic term. Unmatched Capital’s reading is that the seat count to negotiate is the one after the Series B, which no published source cited here measures.

Seniority decides who is paid first in a sale. In a senior structure a later series is paid before an earlier one, and in a pari passu structure the series share. Fenwick’s explainer, from 2012, gives a Series B with a $30 million senior preference taking $30 million of a $40 million sale and leaving $10 million to a $25 million Series A. No current figure on seniority by stage was found.

Pro rata is the right to buy a share of a later round to hold one’s percentage. Y Combinator describes it for SAFE investors as a right, not an obligation, and says that giving it is optional for the company. Fenwick’s explainer also describes pay-to-play, which penalises an investor that does not take its full pro rata share in the next round.

What do Series A and Series B do to ownership and a 1x liquidation preference?

In a hypothetical company, two rounds cut the founders from 75% to 51.6%, and a 1x non-participating preference means a $75 million sale pays the founders 30% of the proceeds. Nothing in this example is a real company or a quoted case, and every figure is Unmatched Capital’s calculation. Before the Series A the founders hold 75%, an option pool 10% and seed investors 15%, who put in $2 million. The Series A is $15 million at a $60 million pre-money valuation ($75 million post-money), which gives the investor the 20% that Y Combinator says a lead generally wants and uses Crunchbase’s median round size. The Series B is $30 million at a $185.2 million pre-money valuation, Cooley’s second-quarter 2026 median, which is $215.2 million post-money and 2.5 times the Series A valuation. Each investor holds 1x non-participating preferred, equal in rank (pari passu). The pool is treated as fully issued, vested and exercised at no cost, which overstates employees’ proceeds, and no pool top-up is modelled.

Ownership	Before Series A	After Series A	After Series B
New investors in the round	none	20.00%	13.94%
Founders	75.00%	60.00%	51.64%
Option pool	10.00%	8.00%	6.88%
Seed investors	15.00%	12.00%	10.33%
Series A investor	none	20.00%	17.21%
Series B investor	none	none	13.94%

A holder with 1.00% before the Series A has 0.80% after it and 0.69% after the Series B if they do nothing. Buying pro rata keeps the 1.00% and costs 1% of each round: $150,000 at the A and $300,000 at the B.

A 1x non-participating holder takes the larger of its money back or its share as converted into common. The preferences total $47 million. Each outcome at six sale prices, in millions of dollars, where the sale price means what is left for shareholders after debt and transaction costs:

Sale price	Founders	Option pool	Seed	Series A	Series B
$30	0	0	1.28	9.57	19.15
$47	0	0	2.00	15.00	30.00
$75	22.50	3.00	4.50	15.00	30.00
$150	72.00	9.60	14.40	24.00	30.00
$215.2	111.12	14.82	22.22	37.04	30.00
$400	206.54	27.54	41.31	68.85	55.76

Below $47 million the preferred holders share everything in proportion to their money, and the common gets nothing. At $75 million the Series A and B investors take their money back, $45 million, because converting would give them less (about $9.0 million and $10.1 million), while the seed converts, because its share of the remaining $30 million, $4.50 million, beats its $2 million. At $75 million, about 65% below the Series B valuation, the founders and the pool hold 58.5% of the company and receive $25.5 million, 34% of the proceeds, while the Series B investor holds 13.94% and takes 40%. At the $215.2 million Series B valuation the Series B investor takes $30 million, which equals its converted share, and above that every holder converts and payouts match ownership. Were the Series B senior, a $30 million sale would pay the B the full $30 million, $10.85 million more than the pari passu split, all of it from the seed and Series A investors, and the common would still receive nothing.

Is Series A or Series B better?

Neither is better, because the label records what a company’s evidence supported when it raised, and the founder does not choose it. A Series B at $185.2 million is not a better outcome than a Series A at $60 million if the company then needs a bridge, and a Series A can be a fine place to stop for a business that can fund itself. Casado’s point above is the same: the letter is a poor proxy for how developed the company is. What can be compared is the cost and the odds. A lead at a Series A generally wants 20% of the company, the Series B round in the example takes 13.94%, and Crunchbase’s count puts the share of boom-era Series A companies that reached a B by August 2024 at just over a third.

What this means for founders and early shareholders

A founder planning the round after seed should plan the Series A, with any committed extension or debt, to reach the close of the Series B, test that plan against the 31-month average gap for US companies in 2024 and against three years, and check it against what a Series B investor will check: a repeatable sale and unit economics. If the pre-money valuation stays at $60 million, the first extra $1 million in the example costs existing holders about 1.05 percentage points, and later millions slightly less. Seniority is worth settling before the Series B valuation is agreed: in the example a senior Series B takes $10.85 million more of a $30 million sale, all of it from the seed and Series A investors, and the founders receive nothing either way.

An early employee holds common stock, which is paid after the preferred. In the example the option pool receives nothing at a $30 million sale and $3.0 million at $75 million, before exercise prices and unvested options, and a holder with 1.00% before the Series A has 0.69% by the Series B. Asking the company for the preference stack and the fully diluted share count is the way to read an option offer against that stack.

An angel deciding whether to follow on can price the pro rata right: $150,000 and $300,000 for each 1.00% held in the example, against Crunchbase’s finding that just over a third of boom-era Series A companies had raised a B by August 2024. Whether the right carries pay-to-play, and what the company’s cash covers, are the questions that decide it. This is general information, not investment advice, from sources that include law firms and venture firms with their own views. More on the asset class is in venture capital.