Startup Option Pool Size: How to Set It and Limit Dilution

A startup option pool is a block of shares reserved for future equity grants to employees, advisors and other service providers. In U.S. priced rounds, HSBC Innovation Banking finds that new or expanded pools most commonly run 10 to 20 percent, but in our view a sensible size is what your hiring plan needs until the next round. Because investors usually require the pool before they invest, it dilutes founders, not new investors.

So the pool isn't a formality. It's part of the price. We'd size it from a real plan and negotiate it alongside the valuation. For comparison outside the U.S., Carta, citing HSBC Innovation Banking's UK-focused Venture Capital Term Sheet Guide 2026 (643 of its 711 term sheets were for UK-headquartered companies), reports that 10 percent is the most frequent pool size and that 71 percent of those term sheets created or topped up a pool.

Definition: An option pool is the number of shares a company's board and stockholders set aside under an equity incentive plan to grant as stock options or other equity awards to current and future team members.

Why your option pool strategy matters

• Recruiting. Early-stage startups rarely match big-company salaries. Equity lets you offer upside instead.
• Retention. Vesting, which Carta describes as commonly four years with a one-year cliff, keeps people aligned over time.
• Investor expectations. Priced-round term sheets commonly specify the size of the unallocated pool after closing. HSBC Innovation Banking's 2026 U.S. Financings Guide, built from more than 500 signed U.S. deals, found that two thirds of rounds create or expand the employee pool.
• Cash efficiency. A thoughtful equity offer can reduce the cash salary needed to land a key hire.

In job descriptions, present equity as a real part of the package and explain it clearly. See how to pay your first 10 employees for a full compensation framework.

How startup option pools work

• A formal plan comes first. The company adopts an equity incentive plan that sets the number of reserved shares. For options to qualify as incentive stock options (ISOs), the Internal Revenue Code requires stockholders to approve the plan within 12 months before or after it is adopted.
• The board approves each grant. An offer letter promising options is not a grant. Under Delaware law and most equity plans, the board approves it, usually in a written consent, with a set exercise price. See the employee equity offer letter guide.
• The Section 409A regulations expect the exercise price to be at fair market value. Most startups rely on an independent 409A valuation. Under Treasury Regulation 1.409A-1, an independent appraisal dated no more than 12 months before the grant is presumed reasonable, and an older value stops being reasonable once information that could materially affect it becomes available. That is why companies refresh their 409A at least yearly and after material events such as a financing.
• ISO limits apply. Under Section 422, ISOs that first become exercisable in a calendar year are capped at $100,000 of stock value (measured at grant), the exercise price cannot be below fair market value, and options cannot run longer than 10 years. Anything above the cap is treated as a non-qualified option. Contractors and advisors can only receive non-qualified options. The IRS explains that ISOs are generally not taxed as ordinary income at exercise but can trigger alternative minimum tax, while non-qualified options are generally taxed on the spread at exercise.
• Unvested shares return to the pool. When someone leaves before vesting, their unvested options typically go back into the pool for reuse, as Carta's guide notes.

How big should your option pool be?

Carta's guidance is that your pool should match your actual hiring plan for the next 12 to 18 months rather than a generic benchmark. We like two methods together: a bottom-up model to set the number, and market data to sanity-check it.

1. Bottom-up hiring model (primary)

1. List every hire you plan before the next round, with timing.
2. Assign an equity range to each role using current benchmarks.
3. Add refresh grants for existing employees and a buffer for a senior hire you did not plan.
4. Total the shares. That is a reasonable starting point for your pool.

The grant percentages above are illustrative only; benchmarks vary widely by stage, location and role, so it is worth checking current market data for your plan.

2. Top-down benchmark (sanity check)

Three current data points frame what investors will expect:

• U.S. rounds: HSBC Innovation Banking's 2026 U.S. Financings Guide says the pools that rounds create or expand are most commonly 10 to 20 percent.
• UK term sheets: Carta, citing HSBC Innovation Banking's UK-focused Venture Capital Term Sheet Guide 2026, reports that pools of 10 to 15 percent are most common there, with 10 percent the most frequent.
• Cap tables: Carta's Founder Ownership Report 2026 puts the median employee pool at 12.1 percent of equity at the seed stage, rising to 16.8 percent by Series C.

If your bottom-up number is far outside that range, recheck the hiring plan. But don't inflate the pool just to match a benchmark. In the illustrative plan above, a 5.5 percent need is a strong argument against a 15 percent top-up.

The option pool shuffle: pre-money vs post-money pools

Carta describes the "option pool shuffle" as the way investors can effectively lower your true valuation by requiring a larger pre-money option pool. The headline number stays the same. What you actually get paid for your shares goes down. A pre-money pool dilutes only existing shareholders; a post-money pool spreads the dilution across everyone, including the new investor. Here it is in numbers.

Worked example (illustrative). An investor offers $2M at an $8M pre-money valuation ($10M post-money) and requires a 10 percent unallocated pool post-closing, created in the pre-money.

• Pool in the pre-money (typical): the investor owns 20 percent, the new pool is 10 percent, and founders keep 70 percent. The founders' shares are effectively valued at $7M, not $8M.
• Pool created after the round (rare): founders would own 80 percent before the pool, and the 10 percent pool dilutes everyone, leaving founders at 72 percent and the investor at 18 percent.

Here is the pre-money case in share counts, assuming the founders hold 8,000,000 shares and there is no existing pool:

The price per share is $0.875 ($8M divided by the 9,142,857 pre-money shares, which include the new pool). The founders' 8,000,000 shares are worth $7M at that price. If the company already had 500,000 unallocated options, the top-up would be 642,857 shares, not a fresh 1,142,857 on top of the existing ones.

The 2 point gap in founder ownership (70 versus 72 percent) on a small round can compound at later stages. Understanding the mechanics of pre-money valuation helps you see the real price in any term sheet.

A simpler example: if founders own 10,000 shares and create a 15 percent pool before any investment, the company issues about 1,765 pool shares, total shares become 11,765, and founders now own 85 percent before a single grant is made.

"It's a couple of points. Just close the round."

We have some sympathy for this one. Our own view, from our take on reading cap tables, is that a point or two of dilution early on is mostly noise, and a founder who stalls a good round over it can lose more than they save.

But the pool fight is rarely about a point. A default 20 percent request against a plan that needs 5.5 percent is a gap of 14.5 points of ownership, carved from the founders' side, and shares nobody needs just sit in the pool until the next round. Give up the point. Push back on the other 14.5.

How to negotiate the option pool with investors

• Bring a hiring plan. In our view, a credible bottom-up model is the strongest answer to a default 15 or 20 percent request.
• Count existing unallocated shares. Often only a top-up is needed, not a new pool from scratch.
• Negotiate the pool and the valuation together. A higher pre-money with a bigger pool can be worth less to founders than a lower pre-money with a right-sized pool.
• Ask what the pool covers. Is it meant to cover refresh grants and executive hires, and through what date? Get the answer in writing.

Common option pool mistakes

• Counting promised offers as granted equity before board approval.
• Granting options without a current 409A, which risks the safe harbor and can create tax problems for employees.
• Forgetting refresh grants, so key people run out of unvested equity after three or four years.
• Oversizing "just in case", which dilutes founders today for shares that may not be used.
• Ignoring post-termination exercise rules. Section 422 generally requires ISOs to be exercised within three months after employment ends to keep ISO treatment, so it is worth explaining this to departing employees.

Managing the pool over time

• Track grants, vesting and remaining shares in a cap table tool (see our guide to cap table management).
• Consider updating the hiring plan and pool forecast before each fundraise.
• Budget refresh grants in annual planning, not only at review time.
• Teach employees how vesting, dilution and exit value work, so equity is valued properly.

The bottom line

Size the pool from the people you plan to hire, not the number an investor opens with. Treat pool and price as one negotiation, and keep the paperwork (board approval, current 409A) clean for every grant. That's our approach; your counsel and investors may reasonably land somewhere else.

The term sheet shows the valuation.

The pool shows what you're really being paid.

Before a priced round, pressure-test how your cap table and hiring plan read to investors. 1752vc's Pitch Deck Analyzer gives AI feedback on your deck, and the remote Accelerate program invests $100K at a valuation cap of up to $3.5M in early-stage startups ready to grow, with founder-led sales training and access to a network of 850+ investors.

Key takeaways

• New or expanded pools in U.S. rounds most commonly run 10 to 20 percent (HSBC Innovation Banking's 2026 U.S. Financings Guide), but we suggest sizing yours from a bottom-up hiring plan to the next round.
• Pools created in the pre-money dilute existing holders, mainly founders, which effectively lowers your valuation.
• It usually helps to negotiate the pool size and valuation together, and to count unallocated shares you already have.
• The 409A regulations point to granting options at fair market value backed by an independent 409A appraisal no more than 12 months old.
• ISOs carry a $100,000 annual exercisability limit, a 10-year maximum term and stockholder plan approval requirements.

Frequently asked questions

How big should a startup option pool be?

HSBC Innovation Banking's 2026 U.S. Financings Guide says pools created or expanded in U.S. rounds most commonly run 10 to 20 percent, and Carta's 2026 founder ownership data shows a 12.1 percent median pool at seed. In our view, a better guide is the number of shares your hiring plan needs for the next 12 to 18 months, including refresh grants and a small buffer.

Does the option pool dilute founders or investors?

When the pool is created or increased in the pre-money, as most term sheets require, it dilutes existing shareholders, mainly founders. A post-money pool, added after the investment, dilutes everyone including the new investors, but that structure is less common. In a $2M round at an $8M pre-money, a 10 percent pre-money pool leaves founders at 70 percent versus 72 percent with a post-money pool.

What is the option pool shuffle?

It is the effect of requiring a larger pre-money option pool, which reduces the value founders receive even though the headline pre-money valuation stays the same. For example, an $8M pre-money with a 10 percent pre-money pool effectively values the founders' shares at $7M.

Do I need a 409A valuation before granting options?

In practice, yes. Section 409A expects options to be granted at fair market value, and an independent appraisal dated no more than 12 months before the grant is presumed reasonable under the Section 409A regulations. Many companies refresh it after a financing or other material event.

Can contractors and advisors receive options from the pool?

Yes, but only as non-qualified stock options, because the tax code limits incentive stock options to employees. Advisor grants are usually small and often vest over a shorter period than employee grants. It is good practice to document each one with a board approval and a written advisor agreement.

Sources

• Carta: Option Pools Guide, How to Size Your Employee Option Pool
• Carta: Founder Ownership Report 2026
• HSBC USA: HSBC Innovation Banking Term Sheet U.S. Financings Guide finds Mega-Rounds Surge While Core U.S. Venture Terms Stabilize
• Cornell LII: 26 CFR 1.409A-1, Definitions and Covered Plans
• Cornell LII: 26 US Code 422, Incentive Stock Options
• IRS: Topic No. 427, Stock Options