Splitting founder equity

The core idea#

The founder split is the first and most emotional financial decision a team makes, and one of the hardest to change later. A good split rewards the work still to be done more than the work already done, reflects real differences in role and commitment, is backed by vesting so that it adjusts if someone leaves, and is agreed in a way every founder can defend for years. In deeptech, the split also has to account for professors who stay in their jobs, inventors who may or may not join, and the university's own stake.

Stage: minus-one to formation · Lens: Core, with deeptech specifics · Reading time: about 30 minutes

Who this is for#

• Founding teams about to incorporate.
• Lab spinouts dividing equity between academics, full-time founders and a business co-founder.
• Founders adding someone after formation.

What you leave with#

• An understanding of what the data and research say about equal and unequal splits.
• A method to reach a split you can explain.
• A worked example for a typical lab spinout team.
• Scripts for the conversation, and a list of what to sign.

What the data says#

Two bodies of evidence matter. Carta's cap-table data shows what founders actually do. The Hellmann and Wasserman research shows what tends to go wrong.

What founders actually do (Carta, US)#

Sources: Carta, February 2026 (40,228 US startups, splits at formation); Carta two- founder teams, June 2026.

The trends that matter:

• Equal two-way splits have become far more common. Carta found that 31.5% of twofounder teams split equally in 2015, rising to 45.9% in 2024 (Carta Founder Ownership Report 2025). Its 2025 figure was 44.6% (Carta).
• Even unequal two-way splits are now close to even. The median two-founder gap narrowed from 57/43 in 2021 to 51/49 in 2025 (Carta).
• Very lopsided splits are rare. Fewer than 5% of two-founder teams split 80/20 or more (Carta).
• Biotech is the exception that matters for deeptech. Across two-founder biotech teams, the lead founder's median was 60% against 40% for the second founder (Carta Founder Ownership Report). Science-led companies more often have one founder who clearly brought the core asset.
• Bigger teams nearly always have a CEO premium. In teams of three to five, the lead founder typically gets at least 10 percentage points more than the next founder (Carta).
• Founders split up more often than you'd think. First-year breakups among twofounder teams rose from 4% to 7.5% over the decade, and somewhat under a quarter split up within four years (Carta Founder Ownership Report). That is the case for vesting, which is covered in 3.06.

What tends to go wrong (Hellmann and Wasserman)#

Thomas Hellmann and Noam Wasserman studied 1,476 founders across 511 US tech and life-science ventures. They found that roughly a third of teams split equally (NBER digest; published in Management Science , 2017). Their findings:

• Differences predict unequal splits. Teams were less likely to split equally when founders differed in who generated the idea, prior founding experience and capital put in. Larger teams and teams with more work experience were also less likely to split equally. Family-related teams were more likely to (HBS Working Knowledge).
• Equal splits came with lower first-round valuations. The effect was concentrated in teams that agreed quickly, in under a day (NBER digest).
• The authors' reading is that the quick handshake is the problem, not equality itself. Equal splits reached after real negotiation did not show the same weakness. In a later summary, Hellmann reported that 42% of teams agreed within a day, and read this as a reluctance to face hard co-founder conversations (Startup Genome, Hellmann).
• The money at stake is large. The authors estimated that stronger founders who accept an equal split leave roughly 10% of the firm's equity on the table, about a quarter of an average founder stake (NBER working paper).
• Equal splits change less often later. A follow-up study of British Columbia startups found that teams starting equal were less likely to change relative stakes (Startup Genome).

The practical takeaway: an equal split is fine, and common, if you get there by honestly comparing contributions. What predicts trouble is splitting 50/50 to avoid the conversation. Investors also treat a sensible, explained split plus vesting as a sign of a team that can handle hard decisions.

Three ways to split, and when each fits#

There is no single right method. There are three families of method, and each fits a different team shape.

1. Equal or near-equal split#

The argument. Michael Seibel's view at Y Combinator is that real co-founders should get equal or near-equal stakes. His reasoning is that almost all the work is still ahead, and early work or the original idea counts for little against the years of execution to come (YC blog). He later framed equality as a rule of thumb rather than a law. He argued that the purpose of founder equity is to keep each founder motivated for the long haul, so being generous is usually the better mistake (YC video, summarised).

When it fits.

• Two or three founders who are all full-time from day one.
• Roles of similar weight, for example CEO and CTO.
• No founder has brought a dominant asset such as the core IP, significant cash or a signed customer.

Watch out for:

• Deadlock in 50/50 teams. Fix it with governance rather than equity: a board, a casting vote for the CEO on operational matters, or a deadlock clause.
• The quick-handshake problem described above. Equal is fine. Equal because no one wanted to talk about it is not.

2. Weighted-factor split#

The idea. List the contributions that matter to this company. Weight each one by how much it matters. Score each founder against each factor. Shares fall out of the arithmetic. Founder equity calculators and many accelerator templates work this way. Their value is that they force the conversation into specifics, not that the numbers are precise.

Typical factors for a deeptech company:

When it fits.

• Teams of three or more.
• Teams with clearly different commitments (one founder still in a lab job, say).
• Spinouts where one person invented the technology.

Watch out for:

• Gaming the weights. Agree the factors and weights first, separately, before anyone scores anyone.
• False precision. Round the result to a split you can explain in a sentence.

3. Dynamic split (Slicing Pie)#

The idea. Mike Moyer's Slicing Pie does not fix percentages on day one. Each person's atrisk contributions are valued at fair market value. That means unpaid salary relative to what they could earn elsewhere, cash, equipment and so on. These are then converted into "slices". Moyer recommends a 2x multiplier for non-cash contributions and 4x for cash, because cash is scarcer (Slicing Pie Handbook, notes; Quartz). Each person's share is their slices divided by the total. The model also defines what happens when someone leaves, depending on why. His core principle is that someone paid a full market salary isn't taking risk, so isn't owed equity (Built In, Moyer).

When it fits.

• Very early, bootstrapped, pre-funding teams.
• Commitments that are uncertain or changing: people trying the idea part-time, or a team still forming.

Watch out for:

• It is not built for venture-backed scale. You will freeze the pie and convert it to a fixed cap table, with vesting, before or at your first priced round. Investors want a clean cap table.
• Tracking overhead. Someone has to keep the ledger honest.
• Legal implementation varies. In India and the UK, shares exist from issue, so a dynamic model needs a contractual mechanism: shares issued later in tranches, or a buy-back from those who earned fewer slices. Get a lawyer to set it up.
• Deeptech fit. Fair market value is hard to set for an inventor's tacit knowledge or a professor's time. Most deeptech teams use Slicing Pie as a temporary tool during a 3 to 9 month minus-one phase, then convert.

Which to use#

Whatever you choose, the most important part is the same: every founder's shares vest . Vesting turns an imperfect split into a fair one over time. See playbook 3.06.

Deeptech specifics: the people who make this hard#

Software teams mostly argue about CEO versus CTO. Deeptech teams have a more complicated cast. Each person below needs a deliberate answer.

The professor or PI who keeps their job#

• The issue. The PI often conceived the research and gives the company credibility, but will stay employed by the university, often under conflict-of-interest rules that cap their time on the company.
• How teams handle it.
  • Give the PI meaningful but clearly sub-full-time founder equity.
  • Make it vest on a schedule tied to their actual role. Spell that role out, for example: chief scientific adviser, two days a month, scientific advisory board chair.
  • Do not give a non-operating PI the largest stake. Investors read that as a sign the company will be run from the lab.
• Check the university rules. Many institutions limit equity, board roles or time for staff (see 2.01 and 2.03). In India, IIT and other institute policies set out what faculty can hold and do.
• Test. If the PI left tomorrow, would the company stall? If yes, they deserve more. If no, they are closer to a senior adviser, and their stake should be in the low-to-mid teens at most, sometimes far less.

The inventor who isn't sure they'll join#

• Being named on the patent does not, by itself, earn founder equity. The university usually owns the patent (2.01), and the company licenses it (2.07). What earns founder equity is future work and the tacit know-how needed to make the technology work.
• If an inventor won't commit, offer:
• an advisory grant (often well under 1%, vesting monthly over two years);
• or a share of the university's inventor revenue, which comes to them through the university's policy, not from your cap table.

The PhD student or postdoc#

• Often the person who actually built the prototype, and the most likely future CTO. Be careful of under-allocation. It is common for the senior person to propose a token 2 to 5%. If they are going full-time and are hard to replace, they are a founder. Treat them as one.
• Check the stipend and visa position. A student on a fellowship or a student visa may not be able to work for or hold shares in the company until they graduate. Plan the timing; don't paper around it.

The business co-founder who joins later#

• Often joins after the minus-one stage, so the scientists feel they have "done the hard part". Remember the Carta and Seibel point: most of the work is ahead.
• A business CEO who joins full-time before the first round is a founder, typically in the same range as the technical lead. If they join after the seed round, they are more likely an executive hire with an option grant (see 3.04 for benchmarks).

The university#

• Keep the university's stake out of the founder-split conversation. Agree it separately as part of the licence (2.07, 2.11).
• Then split what is left among founders.
• Model the final picture with both. The university's share is usually issued without vesting, so it dilutes everyone from day one.

Capital put in by a founder#

• If one founder puts in cash, for lab time or a prototype build, treat that as an investment, not as a reason for more founder shares. Use a SAFE, a convertible note or shares at an agreed price. That way, the money is rewarded as money, and the split

reflects work.

• In India, iSAFE notes or CCPS at a proper valuation do the same job. Talk to your CA about the valuation rules that apply to share issues.

Worked example: a four-person lab spinout#

A fictional battery-materials spinout from an Indian institute. The figures are illustrative.

The team.

Step 1: take the university stake off the top. The licence gives the institute 10% (see 2.11). Founders split the remaining 90%.

Step 2: agree factors and weights first, before scoring.

Step 3: score everyone 0 to 10, on their own, then compare and discuss gaps.

Step 4: compute. Points are each score times its weight, summed.

Step 5: sanity-check the result, then round to a story.

• The model gives Ravi the largest stake. That's defensible: he is full-time, the inventor and the person who makes the process work.

• Asha and Dev come out almost equal. That's the point to discuss. An investor will expect the CEO to carry at least as much as any non-CTO founder. The team agrees to move 3 points from Dev to Asha, reflecting the CEO's accountability for fundraising.

• Menon's stake is meaningful but not controlling. That is what investors want to see from a non-operating PI.

Sensitivity check. If the team instead weighted IP at 30 and commitment at 25, Menon would rise to 18.5% of the founder pool and Asha would fall to 24.3%. Run the alternatives so everyone sees how much the weights matter. Usually the gap is a few points, which makes the final rounding easier to accept.

The final agreed split.

The one-sentence story the team can tell investors: "Ravi and Asha lead and hold the most; Dev built the pilot and is a full founder; Professor Menon's stake reflects his ongoing scientific role at around a day a week; the institute's 10% comes from the licence."

An option pool for the first hires is usually created at or just before the seed round and dilutes everyone, including the institute unless it has anti-dilution protection. See 5.01.

Running the conversation#

The research above is clear: the process matters more than the number. Plan for at least two meetings over a week or more, not a single evening.

Before meeting 1#

1. Each founder writes down, privately:

   • their expected role for the next four years;
   • their time commitment and start date;
   • what they think they have contributed so far;
   • the one outcome that would make them feel the split was unfair.

2. Someone drafts a factor list and weights. Circulate it, unscored.

Meeting 1: agree the rules, not the numbers#

• Agree the factors and weights.
• Agree that everyone vests: four years, one-year cliff, unless there's a reason otherwise.
• Agree how the university stake and any founder cash will be handled, separately.
• Agree what happens if someone goes part-time or leaves. Outline it here; detail it in 3.06.

Between meetings#

Each founder scores everyone, including themselves, on their own.

Meeting 2: compare, discuss gaps, round#

• Put the score sheets side by side. Discuss only where scores differ by 3 or more points.
• Compute, then round to a split everyone can explain in one sentence.
• Each person says aloud whether they can live with it for four years. Silence is not agreement.

Scripts#

Opening meeting 1:

"I want us to get this right rather than fast. The research says teams that agree in a day tend to regret it. Can we agree the rules today, score separately, and settle it next week?"

When a professor expects a large stake:

"Your science is why this company exists, and we want your stake to reflect that. Investors will also look at who is running the company day to day. Could we set your share around your ongoing role, written down, with room to grow if that role expands?"

When a student or postdoc is being underweighted:

"If Dev went back to the lab tomorrow, who would run the reactor? If the answer is nobody, Dev is a founder, and the split should say so."

When someone wants credit for past work:

"What you've done is the reason we're here. But we're signing up for four or more years of work. Can we weight the next four years more heavily than the last one?"

When the conversation stalls:

"Let's each say what number would make us feel taken advantage of. Then let's see whether there's a split that's above everyone's floor."

If it still won't resolve:

• Bring in a neutral third party: an experienced founder, a TTO venture lead or your accelerator partner.
• Or use Slicing Pie for six months and revisit with real contribution data.
• Do not incorporate with the question open.

Making it legal#

This is general information, not legal or tax advice. Use a startup lawyer and, in India, a CA. A split agreed over coffee is worth nothing until it is on the share register with vesting attached. Every jurisdiction needs the same four pieces:

1. Shares issued at a nominal price , as early as possible, before the company has value.

2. Vesting , so unvested shares come back if someone leaves. See 3.06.

3. IP assignment from every founder to the company. This covers pre-incorporation work, separate from the university licence (2.01).

4. A founders' or shareholders' agreement covering roles, decisions, leaver terms and transfer restrictions.

India (private limited company)#

• Issuing the shares. Founders usually subscribe at face value in the memorandum at incorporation. Shares allotted after incorporation must be reported on Form PAS-3 within 30 days (LegalSuvidha).
• Price later issues properly. Once there is a valuation, issuing founder shares cheaply can have tax consequences. Allot early, and ask your CA about the valuation rules that apply.
• Vesting. Indian company law has no built-in concept of unvested shares. Founder vesting is a contractual choice, not a Companies Act requirement (InCorpX).
  • It is usually done as reverse vesting : founders own all their shares from day one, but the company or other founders hold a right to buy back unvested shares, often at face value, if a founder leaves early.
  • The right sits in the shareholders' agreement and the articles, with transfer restrictions (LegalSuvidha; CalcGuru).
  • Put the buy-back right into the articles as well as the agreement. A shareholders' agreement binds only its parties, and clauses inconsistent with the articles can be hard to enforce (Khurana & Khurana).
• Sign before you allot. Applying vesting after shares are issued needs every founder's consent and is procedurally awkward (EquityList).
• Options are for employees, not founders. Promoters generally cannot receive ESOPs, apart from a narrow exception for DPIIT-recognised startups. So founders should hold shares with reverse vesting (echai.ventures). For contributions already made, such as IP, sweat equity shares under Section 54 are an option (InCorpX).

United States (Delaware C-corp)#

• Restricted stock purchase agreement. Founders buy common stock at a fraction of a cent per share, subject to the company's right to repurchase unvested shares.
• 83(b) election. File with the IRS within 30 days of the stock grant. Without it, each vesting tranche can be taxed as income at its value when it vests. Missing the deadline is one of the most expensive and least fixable founder mistakes.
• IP assignment. Each founder signs an invention assignment agreement assigning preformation work to the company.
• If the company is a Delaware parent of an Indian operating company (the "flip"), the split is set at the parent level. Do the Indian side with FEMA advice.

United Kingdom (private limited)#

• Founders subscribe for shares at nominal value at incorporation.
• Vesting is usually done through leaver provisions in the articles and shareholders' agreement. Good and bad leaver categories decide the price at which shares are transferred back.
• Ask your adviser whether a tax election on restricted securities is needed when founder shares are subject to leaver restrictions. In a spinout, the university's investment agreement will often set the template (2.11).

Documents checklist#

Mistakes that cost teams the most#

1. The quick handshake. Agreeing 50/50 in an evening to avoid an awkward talk. It is the pattern most associated with lower valuations in the Hellmann and Wasserman data.
2. No vesting. One founder leaves in month eight holding 30%. That is dead equity on the cap table, and investors will ask you to fix it before they invest.
3. Paying for the past. Overweighting who had the idea or who has been in the lab longest, and underweighting the next four years.
4. The professor as majority holder. A non-operating academic with the largest stake signals a lab project, not a company.
5. The token postdoc. Giving the person who built the prototype 3%, and then losing them to a better offer.
6. Founder cash as founder equity. Money should be rewarded as an investment. Otherwise, a small cheque can quietly buy a large stake.
7. Mixing in the university. Negotiating the founder split and the university stake together. That confuses both conversations.
8. Signing vesting after shares are issued. In India especially, this makes enforcement harder.
9. No deadlock rule in a 50/50 team.
10. Missing the 83(b) deadline (US).

Case note: BharatPe#

BharatPe's shareholders' agreement treated founder shares as restricted, with reverse vesting and a bad-leaver clawback. When co-founder Ashneer Grover left in 2022, the company moved to claw back his restricted shares under that agreement. A separate dispute concerned the face-value price at which he had acquired shares from other founders in 2018 (Treelife; Treelife, bad leaver).

The lesson is not about who was right. Leaver terms, transfer prices and documentation between founders get tested in exactly the situations where relationships have already broken down. Write them while everyone still gets along.

Read next#

• Hellmann and Wasserman, The First Deal (NBER). The research basis for this playbook.
• Michael Seibel, How to Split Equity Among Co-Founders (YC). The case for equal splits.
• Mike Moyer, Slicing Pie . The dynamic model.

Noam Wasserman, The Founder's Dilemmas . Book-length treatment of relationships, roles and rewards.

Related playbooks#

• 2.01 Who owns your invention
• 2.07 Licence anatomy
• 2.11 Spinout equity norms
• 3.04 Business CEO
• 3.06 Founder vesting, cliffs and acceleration
• 5.01 ESOP pool sizing

Sources#

• Carta: Two-founder teams, June 2026
• Carta: Two-founder startups split more equally, February 2026
• Carta: Founder Ownership Report (full)
• Carta: Cofounder equity split data, 2025
• NBER Working Paper 16922: Hellmann and Wasserman
• NBER Digest summary
• HBS Working Knowledge summary
• Startup Genome: Hellmann, How to divide founder equity
• Y Combinator: Seibel on splitting equity
• Quartz: Slicing Pie formula
• Built In: Moyer on fair market salary
• InCorpX: Startup equity structure in India
• LegalSuvidha: Founder shareholding mistakes
• Khurana & Khurana: Founder vesting clauses
• EquityList: Founders' agreement in India
• Treelife: BharatPe and reverse vesting