Down Round Dilution Model: Anti-Dilution, Pools & Waterfalls

A down round isn’t measured by the percentage of new shares issued. It’s measured by what each holder owns—and what each holder can collect when the company is sold.

A financing that issues 50% of the post-round shares, for example, can reduce founder value by more than the headline percentage once an option-pool refresh, anti-dilution protection, pay-to-play terms, and liquidation preferences enter the model.

Key takeaways

• Ownership is only the first layer. A founder can retain 25% of the fully diluted company and still receive little in a modest exit if preferred stock absorbs the proceeds.
• The option pool and anti-dilution terms change the denominator. A pre-money pool refresh and full-ratchet protection can shift substantial value from founders and employees to investors.
• Model the waterfall before signing. Run several exit cases and show proceeds by holder, not just post-money ownership.

Start with the cap table—but don’t stop there

Consider this simplified financing. Before the round, the company has:

The company raises $5 million at $0.50 per share:

New shares = $5M ÷ $0.50 = 10M shares

Before any option-pool refresh, the post-round ownership is:

The round implies a $5 million pre-money valuation and a $10 million post-money valuation. Founders have gone from 60% to 30%.

That arithmetic leaves out the terms that often matter most:

• Unissued shares reserved for future employees;
• Granted and in-the-money options;
• Convertible notes and SAFEs;
• Anti-dilution adjustments;
• Liquidation preference seniority;
• Participation rights;
• Pay-to-play provisions.

A useful model distinguishes issued shares, reserved but ungranted pool shares, and granted options. All three may appear in a fully diluted capitalization table, but they don’t have the same economic status.

The option-pool adjustment

Suppose the investor requires a 15% post-financing option pool. If the pool is added after the financing, let $x$ be the number of new reserved shares:

Pool equation: x / (20M + x) = 15%

The result is approximately 3.529 million shares.

The pool refresh costs founders another 4.5 percentage points. In practice, the important questions are whether the pool is calculated pre-money or post-money, whether existing ungranted options are already included, and whether promised grants are counted.

A pre-money pool generally dilutes existing holders before the new investor buys in. A post-money pool spreads that dilution across the fully diluted company, including the new investor.

Anti-dilution: three outcomes from one down round

Anti-dilution protection changes the conversion price of existing preferred stock when new shares are sold below the old price. It doesn’t create value; it reallocates ownership between holders.

The following examples are deliberately simplified and connect to the original cap table. They ignore the option pool and assume Series A invested $4 million at $1 per share while Series B buys 10 million shares at $0.50.

No adjustment

Without anti-dilution, the original post-round table applies. Founders own 30%, Series A owns 20%, and Series B owns 50%.

Full ratchet

Under full ratchet, Series A’s conversion price resets from $1 to $0.50:

Adjusted Series A shares = $4M ÷ $0.50 = 8M shares

A small issuance at a lower price can trigger the same reset as a large distressed financing, subject to negotiated exclusions and carve-outs.

Broad-based weighted average

Weighted-average protection is less severe because it considers both the size of the new financing and the company’s existing fully diluted capitalization.

New conversion price = Old conversion price × (A + B) / (A + C)

Here:

• A is the existing fully diluted share count;
• B is the number of shares the new money would have purchased at the old price;
• C is the number of shares actually issued in the new financing.

Using the simplified cap table:

• Old conversion price: $1.00;
• A: 10M fully diluted shares;
• B: $5M ÷ $1.00 = 5M shares;
• C: 10M shares issued at $0.50.

The adjusted price is:

$1.00 × (10M + 5M) ÷ (10M + 10M) = $0.75

Series A therefore converts into 5.333 million shares.

The definition of A is critical. If it is described as fully diluted, specify whether it includes the reserved option pool, granted options, warrants, in-the-money convertibles, and other share equivalents. Different definitions can produce materially different adjustments.

The value-transfer comparison

The ownership percentages are easier to understand when paired with proceeds. This simplified comparison assumes a 1x, non-participating preference, no option pool, and conversion whenever it pays more than the preference.

This is the central point: anti-dilution can transfer value even when the company later achieves a healthy exit. The table excludes the option pool and other rights, so a real model will usually show a larger difference.

Liquidation preferences determine who gets paid first

A liquidation preference determines who receives sale proceeds first and how much. A 1x preference usually lets an investor recover its original investment before common holders receive residual proceeds. It doesn’t automatically mean the investor gets 1x and then participates in everything left over.

Assume an investor invested $5 million, owns 25% on an as-converted basis, and the company sells for $12 million.

1x non-participating preferred

The investor compares two choices:

• Take the $5 million preference; or
• Convert to common and receive 25% of $12 million, or $3 million.

The investor takes the preference, leaving $7 million for common holders.

1x participating preferred

The investor first receives $5 million, then takes 25% of the remaining $7 million:

Participation = 25% × $7M = $1.75M

The investor receives $6.75 million and common receives $5.25 million.

The difference is largest at modest exit values. Participating preferred provides downside protection and continued participation in the residual. Some instruments cap that participation at two or three times invested capital.

Seniority matters too. If Series B is senior to Series A, it receives its preference first. If the series are pari passu, they share according to the documents. Accruing dividends, redemption rights, multiple preference stacks, and conversion elections can change the waterfall again.

Market benchmarks are useful only as context. A “standard” 1x non-participating preference may be common in a particular market, but a senior stack, participation rights, or a large pool refresh can make the economics anything but standard. The signed charter and financing documents control.

Pay-to-play changes investor behavior

Pay-to-play provisions require existing investors to participate in a new financing to retain some or all preferred rights. A non-participating investor might:

• Lose its liquidation preference;
• Convert to common;
• Lose anti-dilution protection;
• Lose participation rights;
• Retain only a reduced preference;
• Receive a different security in a recapitalization.

A compact scenario set should include:

Pay-to-play can be healthier than granting inactive investors full-ratchet protection. It directs scarce capital toward investors willing to support the company. The trade-off is that investors unable or unwilling to fund may be pushed into common stock.

For founders, focus on what a non-participant loses, when that loss occurs, and whether partial participation is enough.

Build the model in layers

A practical model can use five calculation layers:

1. Capitalization: common, preferred series, reserved pool, granted options, warrants, SAFEs, notes, and accrued dividends.
2. Financing mechanics: valuation, new money, price per share, new shares, pool size, and pool timing.
3. Anti-dilution cases: no adjustment, weighted average, full ratchet, and pay-to-play outcomes.
4. Waterfall: seniority, participation, caps, conversion elections, and residual common proceeds.
5. Sensitivity analysis: proceeds by holder across several exit values.

Run exits from a low-value sale through a strong outcome—for example, $0, $5 million, $10 million, $25 million, $50 million, $100 million, and $250 million. Report founders, employees, each preferred series, and new investors separately.

Also test the employee pool. A 15% pool is not the same as 15% employee ownership. Some options may be ungranted, unvested, underwater, or valuable only at a high exit. If the down round leaves existing grants below their exercise price, the company may need a new retention plan, creating another dilution event.

Before signing, ask for the fully diluted share-count definition, every anti-dilution exclusion, the preference stack, the treatment of non-participating investors, and a waterfall showing proceeds at realistic exit values. That analysis is more informative than the headline post-money percentage.