Anti-Dilution: Weighted Average vs. Full Ratchet
Note: This is an advanced extension of our venture capital term sheet series. It is intended for founders and executives who have already internalized the conceptual purpose of anti-dilution protection—risk allocation and price protection—and now require a technical understanding of the specific mathematical mechanisms used to reallocate equity in a down-round scenario.
In the previous installment, we established that anti-dilution provisions are forward-looking risk-allocation mechanisms designed to protect an investor’s entry price in the event that the company issues shares at a lower valuation in the future. However, the specific language of a term sheet will dictate exactly how severe that protection is. In venture finance, this severity is governed by a choice between two primary mathematical approaches: Weighted Average and Full Ratchet.
While both mechanisms seek to “true up” an early investor who “overpaid” relative to a subsequent round, they differ radically in their impact on the capitalization table. Understanding the mechanical differences between these two is the difference between a manageable adjustment and a catastrophic loss of founder ownership.
What is the difference between weighted average and full ratchet anti-dilution?
Full ratchet anti-dilution resets an investor’s conversion price to the lowest price of a later round regardless of size, while weighted average anti-dilution adjusts the price proportionally based on how much new capital is raised.
The Hammer: Full Ratchet Anti-Dilution
Full ratchet anti-dilution is the most severe form of price protection available to an investor. It is designed to ensure that if the company issues even a single share at a price lower than what the initial investor paid, that initial investor’s conversion price is immediately and automatically reset to the new, lower price.
Mechanically, full ratchet does not care about the size of the subsequent round. Whether you raise $10 million or $10,000 at a lower price, the result for the protected investor is the same: their stock is effectively repriced downward to match the new issuance. This is often described as a “price reset” rather than an adjustment. Because the investor’s original dollar investment is now divided by a much lower share price, they are issued a significant number of additional shares without being required to contribute any more capital.
Why Full Ratchet is Rare: In modern venture capital, full ratchet is considered extremely “company unfriendly” and is almost non-existent in healthy startup ecosystems. It was briefly popular during the extreme market downturn of 2001–2003, but it has largely been replaced by more balanced formulas. The consequential nature of a full ratchet is that it can “poison” a cap table, making it nearly impossible for a company to raise future capital because the resulting dilution to founders and employees is so extreme that it destroys the management team’s incentive to continue.
The Scalpel: Weighted Average Anti-Dilution
The weighted average approach is the industry standard for anti-dilution protection. Unlike the full ratchet, which only looks at the new price, the weighted average formula takes into account the magnitude of the lower-priced issuance. It considers how many shares were issued at the lower price relative to the total number of shares outstanding.
The weighted average formula is designed to achieve a proportional adjustment. If a company issues only a tiny amount of stock at a lower price, the conversion price for existing investors drops only slightly. If the company raises a massive round at a lower price, the adjustment is more significant.
Within the weighted average category, there are two further sub-varieties that founders must distinguish:
- Broad-Based Weighted Average: This uses a “fully diluted” view of the company—including all issued shares, options, and warrants—as the denominator. This is the most common and founder-friendly version because the larger denominator dilutes the impact of the down-round shares, resulting in a smaller adjustment to the investor’s price.
- Narrow-Based Weighted Average: This calculation is limited to only the currently outstanding issued shares (excluding options and warrants). This smaller denominator makes the adjustment more severe, though still less punitive than a full ratchet.
Mechanical Scenario: The Down-Round Divergence
To illustrate the practical difference in outcomes, consider the following simplified down-round scenario.
The Setup:
- Series A Round: An investor buys 1,000,000 shares at $1.00 per share.
- Total Outstanding Shares: Assume there are 10,000,000 shares total (the investor owns 10%).
- The Down Round: The company hits a difficult market and must raise a “bridge” round to survive. A new investor offers to invest $500,000, but only at a price of $0.50 per share (a 50% drop in valuation).
Outcome 1: Under Full Ratchet
Mechanically, the formula ignores the fact that the company only raised $500,000. It looks only at the $0.50 price. The Series A investor’s conversion price is instantly “ratcheted” down from $1.0 0 to $0.50.
- Because their $1,000,000 investment is now valued at $0.50 per share, the investor is now entitled to 2,000,000 shares instead of their original 1,000,000.
- The Reallocation: The investor has effectively doubled their ownership without writing a new check. These 1,000,000 “new” shares do not come from thin air; they are “squeezed” out of the founders’ and employees’ remaining ownership.
Outcome 2: Under Weighted Average (Broad-Based)
Mechanically, the formula looks at the $500,000 in the context of the entire $10,000,000 company value. It asks: “How much did this $500,000 investment actually move the needle on the company’s weighted price?”
- Since the new issuance represents only a small portion of the total company, the “New Conversion Price” will not drop to $0.50. Instead, it might drop to approximately $0.95.
- The investor is now entitled to roughly 1,052,631 shares ($1,000,000 divided by $0.95).
- The Reallocation: The investor receives an additional 52,631 shares to compensate for the price drop. While this still dilutes the founders, the impact is roughly 19 times less severe than the full ratchet outcome.
Impact on Stakeholders
The mechanical choice between these provisions creates a fundamental shift in how risk is distributed:
- Founders and Employees: Under a full ratchet, the common stockholders bear 100% of the economic burden of the price drop. Under weighted average, the burden is shared more equitably, as the adjustment is limited to the actual economic impact of the new money.
- Existing Investors: Those with full ratchet protection are effectively “immune” to the risks of a down round, as they will always be made whole to the lowest possible price. This can sometimes lead to aggressive behavior where existing investors allow a down round to happen specifically to trigger their ratchet and seize more of the company.
- New Investors: New investors in a down round often view a “full ratchet” held by an old investor as a “smoking gun” on the cap table. They may refuse to invest unless the old investor agrees to waive their ratchet or convert it into a weighted average adjustment to ensure the cap table remains rational and the management team stays motivated.
Summary of Mechanical Outcomes
Full ratchet anti-dilution provides absolute price protection, resulting in a dollar-for-dollar share increase regardless of the size of the financing. Weighted average anti-dilution provides proportional price protection, resulting in a share increase that reflects the actual economic weight of the new investment.
Because of the extreme and often unintended consequences of the full ratchet, it remains a rare “red flag” term that founders should identify immediately during a term sheet review. Most sophisticated deals will default to a broad-based weighted average calculation to maintain long-term alignment between all parties on the cap table.
Anti-dilution mechanics are highly sensitive to the current state of your capitalization table, the specific size of your option pool, and your prior financing history. These formulas should be modeled in detail within your specific cap table to understand the potential impact of various “what-if” down-round scenarios; you can book a confidential consultation for a detailed scenario review.
Liquidation Preference Math: How Outcomes Actually Change