Option Pool Dilution

How Does Option-Pool Dilution Work?

Carta's Q1 2025 private-market report offers a useful reminder that option-pool expansion sits alongside financing dilution rather than replacing it. The percentage sold in a financing changes with valuation, round size, and market conditions; the option-pool treatment is a separate layer in the ownership bridge. A cap-table model should isolate new-investor issuance, pool expansion, and convertible-security conversion instead of combining them into one unexplained percentage.

Carta reported that median Series A dilution was 17.9% in Q1 2025, down from 20.9% one year earlier. Those figures describe total round dilution in Carta's dataset, not an option-pool benchmark.

What an Option Pool Represents

An option pool is a reserve of equity that a company may use for future awards. It may support employee, executive, advisor, or consultant grants, subject to the governing plan and approvals.

Granted awards: Options or other awards already promised to recipients.
Available pool: The unused reserve that remains available for future grants.
Fully diluted capitalization: A broader ownership denominator that may include issued shares, outstanding awards, the available pool, warrants, and convertible securities under the transaction definition.

A market benchmark can help, but it is only a starting point. Carta describes about 10% of company shares as a common rule of thumb, while emphasizing that actual pools vary. A hiring forecast should decide whether that example is too large, too small, or appropriate.

The practical distinction is between the total plan reserve and the amount still available. A company with a 12% plan but only 3% unallocated does not have 12% of unused hiring capacity.

Where the Dilution Enters

The phrase "10% post-close pool" does not identify who pays for it. The term sheet and pro forma need to state when the shares enter the denominator used to calculate the financing price.

With 10 million existing shares, a $40 million pre-money valuation, a $10 million investment, and a 10% available post-close pool funded pre-money, existing holders retain 70%, the investor receives 20%, and the pool represents 10%. The pool top-up lowers the financing price from $4.00 to $3.50 per share.

Who Absorbs the Pool Top-Up?

Moving the same 10% pool from pre-money to post-money shifts 2 percentage points of post-close ownership from the new investor to existing holders in this simplified example.

Ownership comparison Calculated example

Pre-money pool top-up Existing holders: 70% New investor: 20% Available pool: 10% Financing price: $3.50 per share

Post-money pool top-up Existing holders: 72% New investor: 18% Available pool: 10% Financing price: $4.00 per share

View calculation data and assumptions

Calculation inputs and post-close ownership for pre-money and post-money option-pool top-ups
Item	Pre-money top-up	Post-money top-up
Existing shares before financing	10,000,000	10,000,000
Pre-money valuation	$40,000,000	$40,000,000
New investment	$10,000,000	$10,000,000
Target available pool after closing	10%	10%
New pool shares	1,428,571	1,388,889
Financing price per share	$3.50	$4.00
New investor shares	2,857,143	2,500,000
Existing-holder ownership	70%	72%
New-investor ownership	20%	18%
Available-pool ownership	10%	10%

Assumptions: No existing available pool, granted awards, SAFEs, notes, warrants, transaction costs, or fractional-share constraints. Percentages are shown on a simplified fully diluted basis.

Source and method: Frontierspace calculation using the stated inputs. The pricing treatment is consistent with the pre-money and post-money mechanics described in Carta's valuation guide. Actual definitions and approvals depend on the legal documents.

Build the Pool From the Hiring Plan

A defensible pool begins with the equity budget required to reach the next credible financing or operating milestone.

List planned roles: Include expected hiring date, level, function, and location where relevant.
Estimate each grant: Use comparable compensation data, then adjust for stage, cash compensation, and role scarcity.
Add refresh and promotion grants: Existing employees may require equity as responsibilities expand or earlier awards vest.
Reconcile the unused balance: Only the incremental top-up should enter the financing bridge.
Test time to the next round. A pool designed for 24 months of hiring is different from one intended to last only 12 months.

A buffer can be sensible because hiring plans change. But a large unexplained buffer transfers value away from existing holders without proving that the extra reserve will support the company.

Read the Term Sheet and Pro Forma Together

The drafting can matter as much as the stated percentage. Rebuild the transaction from the definition of fully diluted capitalization through the final post-close ownership table.

Confirm whether "10%" means the total post-close available pool or a new 10% issuance on top of the existing reserve.
Determine which awards are already included in outstanding shares and which remain in the available pool.
Model SAFEs, notes, warrants, and accrued interest under their actual conversion terms.
Check whether the calculation includes only common shares or all securities on an as-converted, fully diluted basis.
Confirm the board, shareholder, plan, and securities-law steps with qualified counsel in the relevant jurisdiction.

The difference is easier to see in practice. A holder starting at 5% who absorbs 15% dilution and later 20% dilution retains 3.4% before any pro rata investment: 5% multiplied by 85% and then by 80%. The dilution rates compound rather than add.

What Investors Should Test

For an LP, co-investor, or secondary buyer, option-pool analysis connects company hiring needs with ownership and return sensitivity.

Reconcile issued shares, every award status, the unused pool, convertibles, warrants, and share classes.
Compare grants made, forfeitures returned, and remaining capacity with the hiring forecast.
Model additional rounds and later pool increases, including cases where the investor does not exercise pro rata rights.
Exit ownership: Carry the ownership bridge through the expected financing path rather than applying one generic dilution assumption.
Determine who approves expansions and whether investors receive timely cap-table updates.

The investor's entry percentage is only one point in time. The more useful question is how much ownership may remain when the company reaches liquidity, and what additional capital would be required to defend it.

Including the Hiring Plan in the Ownership Calculation

In our review, we view option-pool diligence as part of deal-specific review rather than a standalone administrative check.

Start with the operating plan: Hiring needs should explain the reserve.
Price, security, convertibles, and the option pool should reconcile to the same fully diluted ownership table.
Model ownership at exit: Later financings and pool increases may matter more than the entry cap table suggests.

The objective is not to minimize the pool at all costs. It is to fund the team the company needs while making the allocation of dilution visible and supportable.

Frequently Asked Questions

Does an option pool dilute investors?

The decision period and the investment period are not the same. A pool created or expanded before the financing price is calculated normally dilutes existing holders. An increase after closing generally dilutes all holders, including the new investors, unless the documents provide otherwise.

Is a 10% option pool standard?

It is a common example, not a universal answer. The appropriate size depends on the unused balance, hiring plan, expected grants, refresh needs, company stage, and time to the next financing.

Do ungranted options count as dilution?

They may count in the fully diluted denominator used to price a financing even though no employee holds them yet. The exact treatment depends on the transaction definition and legal documents.

How should an investor model option-pool dilution?

Start with the current fully diluted cap table, add only the required pool top-up, model convertibles and new investor shares, and then test later financings with and without pro rata participation. Qualified legal and tax advisers should review investor-specific consequences.