Startup Equity Guide: Founder Splits, Vesting & Dilution

Your Job Is to Grow the Pie, Not Just Your Slice

Equity is ownership, represented by shares. But thinking of it as a fixed pie is where founders go wrong. Your job isn't to hoard 100% of a tiny pie; it's to grow the entire pie so enormously that your remaining 15% slice is worth a fortune. How? By strategically selling ownership to get the fuel you need to grow.

You'll give equity to two groups: investors (for cash) and employees (for talent). Managing this is a core founder skill. Getting it wrong leads to co-founder disputes, a crippled ability to hire, and failed funding rounds. Getting it right aligns everyone on the same goal: making the company more valuable.

Founder Equity: Your First and Hardest Negotiation

When you incorporate, you and your co-founders own 100% of the company. Your first big test is deciding how to split that ownership.

Don’t Default to 50/50

It feels fair and easy, but a 50/50 split is often a mistake. It assumes all contributions—past, present, and future—are equal. They rarely are. An unequal split, like 55/45 or 60/40, is often more equitable and prevents future resentment. Have the hard conversation now, not when you're fighting over a term sheet.

Past Contributions: Who came up with the initial idea? Who built the prototype or wrote the first lines of code? Who put in cash to get things started? · Future Contributions: Who has the track record to be CEO and raise capital? Who is the technical lead who will build and manage the engineering team? Are there large differences in market-rate salaries for your respective roles? · Commitment Level: Is everyone quitting their job and going full-time on day one? If someone is keeping their job for six months, their vesting should probably start later.

The Non-Negotiable: 4-Year Vesting with a 1-Year Cliff

This is the most important mechanism to protect the company. All founder shares must be subject to vesting. The market standard is ironclad: a four-year schedule with a one-year cliff.

How it works: You earn no shares for the first 12 months. On your one-year anniversary (the "cliff"), 25% of your shares vest. The rest vest in equal monthly installments for the next 36 months. · Why it's critical: If a co-founder leaves after six months, before the cliff, the company can reclaim all their unvested shares for a nominal price. Without vesting, they'd walk away with a huge chunk of your company, making it nearly impossible to raise money or hire key people.

CRITICAL: File Your 83(b) Election within 30 Days

This is the most common and disastrously expensive mistake founders make. When you receive your founder stock (which has a very low value at incorporation), you have a 30-day window to file an 83(b) election with the IRS.

Filing it tells the IRS you want to pay income tax on the value of your stock now, when it’s worth practically nothing. If you fail to file, the IRS will tax you on the value of your stock as it vests. As your company grows, this can lead to a crippling tax bill in the tens or hundreds of thousands of dollars on phantom income you haven't received.

Do not miss this deadline. Talk to your lawyer, sign the form, and mail it via certified mail the day you incorporate.

Investor Equity: Selling Ownership to Fuel Growth

To scale, you need capital. You get it by selling equity to investors. This process is called dilution.

How Dilution Works: A Tale of Two Valuations

Example: You want to raise a $2M seed round. An investor agrees your company is worth $8M before their investment (the "pre-money valuation"). Your "post-money valuation" becomes $10M ($8M pre-money + $2M investment). The investor’s $2M now owns 20% of that $10M company ($2M ÷ $10M). You, your co-founders, and your employee option pool have been diluted. Your collective ownership has shrunk from 100% to 80% of a more valuable company.

The SAFE Trap: Understand “Post-Money” Caps

In your earliest stages, you'll likely raise on convertibles like SAFEs (Simple Agreements for Future Equity). They are simpler than a priced round, but they contain a hidden trap: the "post-money" SAFE.

Let's say you raise $1M on SAFEs with a valuation cap of $10M. You then go to raise your seed round. Here's the difference:

With Pre-Money SAFEs: The $1M in SAFEs converts as part of the new round's money. Your pre-money valuation is $10M, and dilution is clean. · With Post-Money SAFEs: The SAFEs convert before the new money comes in, changing the denominator. That $1M in SAFEs converts into a chunk of ownership first, diluting the founders, and then the new priced round investors invest. This means the founders experience significantly more dilution than they expected.

The takeaway: Always model out SAFE conversions on your cap table. Y Combinator, the creator of the SAFE, has now switched back to pre-money SAFEs as the default because the post-money version was so founder-unfriendly. If an investor insists on a post-money SAFE, understand the math and push for a higher valuation cap to compensate for the extra dilution.

A Realistic Dilution Path

Expect to sell 15-25% of your company in each funding round. A typical founder ownership path looks like this:

Incorporation: Founders own 100%. · Seed Round: Founders own ~45-55% (after the new raise and option pool). · Series A: Founders own ~30-40%. · Series B: Founders own ~20-30%.

Your percentage will go down, but the goal is for the absolute value of your stake to go up dramatically.

Employee Equity: Your Most Powerful Hiring Weapon

You can't match Google's salary, but you can offer something they can't: a meaningful ownership stake in a high-growth company. This is done through an Employee Stock Option Pool (ESOP).

The Option Pool: Carve It Out Pre-Money

Before a priced round, investors will require you to set aside a block of shares (typically 10-20% for a seed-stage company) for future hires. A key negotiation point is that this pool must be created from the pre-money valuation. This means the founders and any prior investors are diluted to create it. If an investor tries to make you create the pool from the post-money, they are tricking you into bearing the entire dilution yourself.

How Big Should a Grant Be? Benchmarks You Can Use

Provide grants based on the value and seniority of the role, and the stage of the company. An engineer joining when it's just three of you in a garage deserves more than one joining post-Series A with 50 employees.

First 10 employees (esp. engineers): 0.5% - 2.0% · VP / C-level hire: 1.5% - 3.0% · Director-level hire: 0.8% - 1.5% · Senior IC (post-Series A): 0.2% - 0.7% · Advisors: 0.1% - 0.5%, vesting over 1-2 years. Anyone asking for more is a red flag.

Communicate Equity in Dollars, Not Just Percentages

A percentage is abstract and shrinks over time. A dollar value is concrete. When you make an offer, translate the equity into its potential financial value. Get a 409A valuation to set your strike price, then use your last round's valuation to frame the offer.

Example Script: "We're offering you options to purchase 50,000 shares, at a strike price of $0.20 per share. Based on our recent seed funding round, the preferred share price is $2.00. This means the current value of your grant is $90,000 (($2.00 - $0.20) 50,000). Of course, we all believe the company's value will grow significantly, and so will the value of your options."

The Most Common (and Costly) Equity Mistakes

Forgetting the 83(b) Election. You get hit with a six-figure tax bill on phantom income because you missed a 30-day window. Fix: File it the day you incorporate. No exceptions. · The "Fair" 50/50 Split That Turns Toxic. Your co-founder contributes less but owns half the company, breeding resentment. Fix: Use a contribution-based framework to determine the split. · Getting Wiped Out by Post-Money SAFEs. You sign a flurry of SAFEs and are shocked to find your ownership cut in half at your priced round. Fix: Model every SAFE on a cap table. Insist on pre-money SAFEs or a higher cap. · Giving Advisors 1% For a Few Intros. Equity is for building, not just advising. Fix: Stick to the 0.1-0.5% range over a shorter vesting schedule (1-2 years). · Botching the Equity Conversation. A new hire feels misled because their "1%" turned out to be options representing 0.4% after the pool was expanded. Fix: Be radically transparent. Use dollar values and explain dilution.

How to Apply This This Week: Your Equity Action Plan

1. Have the Founder Split Conversation. Use the checklist in this article to have a structured, adult conversation about who gets what and why. Document the rationale. · 2. File Your 83(b) Election. If you incorporated in the last 30 days and haven't done this, stop everything and do it now. Consult your lawyer and use certified mail. · 3. Build a Real Cap Table Model. Open a spreadsheet. List the founders. Add a 15% option pool. Model three SAFE notes converting at different caps. Then model a $2M seed round at an $8M pre-money valuation. Don't stop until you understand exactly where every share goes. · 4. Draft Your First Offer Letter Equity Clause. Write out the script for explaining options to a candidate, using dollar values. Put it in your offer template so you use it every time.