Anti-Dilution Weighted Average: Weighted-Average vs Full-Ratchet Explained With Numbers

Anti-dilution weighted average protection is the mechanism that determines how much an investor’s shares increase when a startup raises a down round at a lower valuation. It exists to protect early investors from seeing their ownership eroded when subsequent rounds price the company below what they originally paid. For GCC founders navigating term sheets, understanding how weighted-average anti-dilution works — and how it compares to the harsher full-ratchet alternative — is essential before signing any priced round. This article explains the maths with worked examples, shows where founders get hurt, and outlines the negotiation tactics that protect your equity.

What is anti-dilution weighted average protection?

Anti-dilution weighted average protection adjusts an investor’s conversion price downward when the company issues new shares at a price below what the investor originally paid. Rather than resetting the price entirely to the new lower figure, the weighted-average method blends the old price and the new price proportionally, weighted by the number of shares outstanding at each price. The result is a moderate adjustment that compensates the investor without inflicting maximum dilution on founders.

The formula is: Adjusted Conversion Price equals Original Price multiplied by (A plus B) divided by (A plus C), where A is the total shares outstanding before the down round, B is the amount of money the original investment would have bought at the original price, and C is the amount of money actually raised in the down round. In plain terms, the bigger the down round relative to the company’s existing share count, the larger the adjustment — but it is always proportional, not absolute. Per the National Venture Capital Association, broad-based weighted average is the standard anti-dilution provision in approximately 90 per cent of US venture rounds, and GCC markets are converging toward the same norm as the ecosystem matures.

How does full-ratchet anti-dilution differ from weighted average?

Full-ratchet anti-dilution resets the investor’s conversion price entirely to the new lower price, regardless of how many shares are issued in the down round. If an investor bought shares at $10 and the company later raises at $2, the full-ratchet adjustment drops the conversion price to $2 — the investor now receives five times as many shares, irrespective of round size. Weighted average, by contrast, would produce an intermediate price depending on the relative size of the down round.

The distinction matters enormously for founders. Full ratchet is punitive because it ignores dilution proportionality. A tiny bridge round at a low price triggers the same adjustment as a massive equity raise. Per Fenwick & West’s 2024 Silicon Valley venture survey, full ratchet appeared in fewer than 8 per cent of seed-stage rounds and approximately 15 per cent of Series A rounds, typically where investors demanded additional protection due to high perceived risk. The OECD venture policy framework recommends weighted-average as the standard anti-dilution mechanism for mature startup ecosystems. In GCC markets, where investor familiarity with standardised terms varies, full ratchet appears more frequently than in the US, making it a critical term to scrutinise. Our cap table guide explains how these adjustments cascade through your equity structure.

What does anti-dilution weighted average look like in a worked example?

Consider a startup that raised $1 million on a $5 million pre-money valuation, giving the investor a 20 per cent stake at $5 per share (200,000 shares). The company later raises a down round of $500,000 at a $2 million pre-money valuation ($2 per share). Under broad-based weighted average, the formula produces an adjusted conversion price of approximately $4.33 per share, compared to the original $5. The investor’s 200,000 shares now convert as though they were purchased at $4.33, netting them approximately 230,947 shares — an increase of roughly 30,947 shares.

Under full ratchet, the same investor’s conversion price drops to $2, yielding 500,000 shares — a 150 per cent increase. The table below compares the two mechanisms side by side for the same scenario.

The difference is stark. Weighted average adds roughly 3 per cent of additional founder dilution, while full ratchet adds approximately 30 per cent. For a founder who owns 60 per cent of the company pre-down-round, full ratchet could reduce their stake by nearly half in a single event. This is why experienced founders treat the anti-dilution mechanism as a non-negotiable term sheet point.

What is broad-based weighted average and why does it matter?

Broad-based weighted average is the most founder-friendly version of weighted-average anti-dilution. The “broad-based” refers to the denominator in the formula: it includes all shares on a fully diluted basis — common shares, options, warrants, and the shares issuable upon conversion of all outstanding convertible instruments. This produces a larger denominator, which dampens the adjustment and results in a higher adjusted conversion price for the investor.

Narrow-based weighted average, by contrast, uses a smaller denominator (typically just the preferred shares outstanding), producing a steeper adjustment that benefits the investor. The practical difference can be significant. On the same $1 million investment at $5 per share with a $2 per share down round, narrow-based weighted average might produce an adjusted price of $3.80 versus $4.33 for broad-based — meaning founders give up roughly 5 percentage points more equity. Per Cooley GO’s standard term sheet library, broad-based weighted average is the market standard at Series A and beyond, but seed-stage investors sometimes push for narrow-based. Founders should always insist on broad-based. Our guide to SAFEs versus convertible notes covers anti-dilution provisions in early-stage instruments.

When does anti-dilution weighted average actually trigger in a down round?

Anti-dilution triggers when the company issues new equity at a price below the investor’s existing conversion price. This is the definition of a down round. The trigger is the issuance itself, not the company’s overall performance. Even a small bridge round priced below the last round activates the anti-dilution provision for all series of preferred stock that carry the clause. SAFEs and convertible notes have their own conversion mechanics, but the principle is the same: if the conversion price is higher than the new round price, the investor benefits from the adjustment.

Founders should understand that anti-dilution applies to every investor who holds the provision, not just the lead. If five angels each invested on a term sheet with weighted-average anti-dilution, all five benefit from the adjustment at a down round. The cumulative dilution to founders can be severe if the down round is deep. Per Harvard Business School’s analysis of failed startups, approximately 35 per cent of seed-stage companies that survive to Series A experience at least one down round, making anti-dilution a live issue rather than a theoretical one. Our pre-seed funding guide covers how term sheet protections evolve across rounds.

How should founders negotiate anti-dilution provisions in GCC term sheets?

Start by insisting on broad-based weighted average, which is the market standard and the most founder-friendly option. If an investor pushes for narrow-based or full ratchet, ask why — the answer reveals their risk assessment of your company. If the concern is a specific risk factor, address it with a board seat, information rights, or a milestone-based tranche rather than a punitive anti-dilution mechanism.

Second, negotiate a pay-to-play provision alongside the anti-dilution clause. Pay-to-play requires existing investors to participate in the down round to maintain their anti-dilution protection. This prevents investors who contributed nothing to the rescue from benefiting from the adjustment. Third, request a carve-out for employee option pool increases, which should not trigger anti-dilution. Fourth, cap the maximum adjustment — a ceiling that limits the conversion price reduction to a defined percentage protects founders from extreme scenarios. Per Orrick’s term sheet database, these four negotiation points appear in approximately 60 per cent of well-negotiated seed rounds. Our reasons VCs reject deals resource explains how unfavourable terms affect future fundraising.

“Anti-dilution is where founders lose equity they did not plan to lose. The weighted-average mechanism is fair; full ratchet is a penalty. Know which one your term sheet carries before you sign.”

How does anti-dilution weighted average affect your cap table over multiple rounds?

Each down round with weighted-average anti-dilution compounds the dilution to founders. If a company experiences two consecutive down rounds, the adjustment applies sequentially: the first adjustment recalculates the conversion price, and the second adjusts from the already-adjusted price. The cumulative effect can reduce founder ownership by 15 to 25 percentage points across two down rounds, depending on the depth of each. This is why tracking your cap table through every scenario — including two or more down rounds — is essential before signing any term sheet with anti-dilution provisions.

Founders should model three scenarios before every priced round: an up round (no trigger), a modest down round (10 to 20 per cent lower valuation), and a deep down round (50 per cent or more lower). The difference between weighted average and full ratchet is manageable in a modest down round but devastating in a deep one. Our cap table guide provides templates for modelling these scenarios. For GCC founders, the Sijilat platform in Bahrain and equivalent registration portals in the UAE require accurate share counts at every issuance, making cap table accuracy a regulatory requirement as well as an investor expectation. The venture studio equity and terms article covers how studio-backed companies structure anti-dilution differently.

Frequently asked questions about anti-dilution weighted average

What is anti-dilution weighted average protection?

Anti-dilution weighted average protection adjusts an investor’s conversion price downward when a startup issues shares at a lower price in a future round. The weighted-average method blends the old price and the new lower price proportionally, producing a moderate adjustment that protects investors without excessively punishing founders.

How does weighted average differ from full ratchet?

Full ratchet resets the conversion price entirely to the new lower price, regardless of how many shares are issued. Weighted average factors in the size of the down round relative to outstanding shares, producing a smaller adjustment. Full ratchet is harsher on founders and is less common outside Series A.

When does anti-dilution protection trigger?

Anti-dilution triggers when a startup issues equity at a price below the investor’s original conversion price. This is called a down round. The mechanism adjusts the investor’s conversion price so they receive more shares, compensating for the lower valuation.

Can founders negotiate anti-dilution terms?

Yes. Founders can push for broad-based weighted average, which is the most founder-friendly standard. They should resist full ratchet unless necessary to close a critical round. The anti-dilution provision is a standard term sheet clause that is almost always negotiable at pre-seed and seed stages.

Anti-dilution weighted average is the standard mechanism that protects investors during down rounds, and understanding its maths gives founders the leverage to negotiate fair terms. Model every scenario, insist on broad-based, and never sign a term sheet without understanding how the adjustment cascades through your cap table. For founders seeking pre-seed funding with transparent, founder-friendly terms, Apply for pre-seed funding at Valu.vc — we deploy $50K–$150K cheques on post-money SAFEs with a five-day response SLA.