Anti-Dilution Protection Explained: Down Rounds

Valuations reset hard across several sectors through the 2024-2026 funding cycle, and plenty of companies that raised at generous prices in 2021 have had to go back to market at a lower one. That's a down round, and it's the single event that activates anti dilution protection — a term sheet clause most founders sign without reading closely, because at the time it looks like it only concerns the investor.

It doesn't. This post covers what triggers the clause, the two mechanisms behind it — full ratchet and weighted average — and a worked example showing the real share-count impact.

What actually counts as a down round

A down round is a new financing round priced below the pre-money valuation implied by the previous round's conversion price. If a Series A priced shares at $1.00 and a Series B later prices them at $0.50, that's a down round for anyone still holding Series A preferred. The trigger isn't the company's total valuation in isolation — it's the per-share price, compared directly against what earlier investors paid to convert. A round can carry a higher post-money headline number than the last one and still be a down round underneath, if enough new shares were issued to get there; the price per share is what the anti-dilution formula actually reads, not the valuation press release.

Why anti dilution protection exists at all

Preferred stock investors negotiate anti dilution provisions because a down round otherwise leaves them holding the same number of shares at a lower implied value, with no recourse. The clause doesn't stop the down round from happening. It adjusts the conversion price those investors use when their preferred stock converts to common, so their as-converted ownership grows to partly offset the price cut. It's a common feature of NVCA-style model financing documents, and it's worth reading the actual NVCA term sheet language rather than assuming every deal uses identical wording.

Full ratchet: the blunt version

Full ratchet anti-dilution is the simplest mechanism and the harshest. It resets the earlier investor's conversion price directly to the new round's price, full stop — it doesn't matter whether the down round issued ten shares or ten million. One cheap share at the new price is enough to trigger the full reset. That makes it extremely founder-unfriendly, because the extra shares it hands the earlier investor bear no relationship to how much actual dilutive stock was issued. Full ratchet clauses do still appear, mostly in distressed or investor-favourable deals, but they're the exception rather than the market default.

Where full ratchet does still turn up is in situations where the earlier investor has real leverage: a rescue financing where the company needs the round to survive, an insider-led bridge with few other bidders, or a market where a particular sector has cooled enough that investors can simply ask for it and get it. Outside those settings, most investors don't push for full ratchet, partly because it's punitive enough to damage founder morale and retention right when the company needs both, and partly because later investors doing diligence on the cap table tend to view a full ratchet clause as a red flag about how the last round was negotiated.

Weighted average: the market standard

Weighted-average anti-dilution is the mechanism most term sheets actually use, and it comes in two flavours: broad-based and narrow-based. Both blend the old conversion price and the new, lower price using a formula, so the adjustment scales with how much cheap stock was actually issued rather than resetting everything to the new floor. The difference between the two flavours is how big a share base that blend is weighted against, and that difference is what decides how investor-friendly or founder-friendly the outcome ends up being.

Broad-based vs narrow-based

Broad-based weighted average uses the fully diluted share count as its denominator — common stock, all preferred as-converted, and the option pool, whether or not those pool shares have been granted yet. That's the largest possible base, which softens the adjustment and is why broad-based is the market default in most venture financings. Narrow-based weighted average uses a much smaller denominator, typically only outstanding preferred stock, sometimes with common stock but almost never the unallocated option pool. A smaller denominator means the same down round produces a bigger price cut, because the new dilutive shares carry proportionally more weight against a smaller starting base. Narrow-based still lands well short of full ratchet's severity, but it's meaningfully more expensive for founders than broad-based on an identical round. Legal reference sites like Cooley GO walk through the exact model-document language if you want the clause text itself.

Working through a real adjustment

Take a Series A investor who put in $2,000,000 at a $1.00 conversion price, giving them 2,000,000 preferred shares. Before the down round, the company has 10,000,000 fully diluted shares outstanding. A Series B then raises $1,000,000 at a new price of $0.50 per share — a clear down round relative to the $1.00 the Series A paid.

Full ratchet vs broad-based, same round

Run that identical Series B through a full ratchet clause instead, and the gap becomes obvious. Full ratchet ignores how small the down round was relative to the existing cap table — it simply resets the Series A conversion price to the Series B price of $0.50, full stop.

Where the extra dilution lands

The Series A investor's extra shares — 181,818 under weighted average, 2,000,000 under full ratchet — don't come from nowhere. They're new shares issued to the earlier investor at no additional cost, which means every other shareholder's percentage of the company shrinks to make room. That's the part of anti dilution protection founders tend to miss when they're focused on the new round's headline terms: the down round dilutes everyone once through the new money raised, and then dilutes founders and common stockholders a second time through the anti-dilution adjustment itself. Understanding equity dilution as a two-step process, not one, is the difference between a term sheet that looks manageable and one that quietly isn't.

It's also worth being precise about who absorbs that second step. Preferred stockholders with their own anti-dilution rights are largely protected from it by definition — the whole point of the clause is to shield them. Common stockholders, including founders and employees holding options, have no equivalent mechanism. Their percentage simply falls to accommodate both the new investor's shares and the anti-dilution top-up on the old preferred, with nothing pushing back in the other direction.

A pattern we see often

A Series A company we've seen run this scenario had raised $4,000,000 at a $1.20 conversion price two years earlier. A subsequent bridge-into-Series-B priced new shares at $0.70 — a real down round driven by a sector-wide reset rather than anything company-specific. Their Series A investors held broad-based weighted-average protection, which cut their conversion price to roughly $1.00 and added a meaningful but survivable block of shares to their position. Founders modelled the same round with a hypothetical full ratchet clause first, purely to see the difference, and the founder-side dilution nearly tripled. That comparison — not the down round itself — was what made the anti-dilution mechanism the actual negotiating point in the next financing, rather than the headline valuation.

What's genuinely negotiable

Removing anti dilution protection entirely from a priced round is rarely realistic; investors expect some form of it as standard. What is worth pushing on is which mechanism applies, and which issuances are carved out of triggering it at all. Common carve-outs worth asking for include:

• Shares issued from an approved option pool top-up, so routine hiring grants don't themselves trigger a reset
• Shares issued on conversion of existing SAFEs or convertible notes already on the cap table
• Shares issued in a board-approved acquisition, merger, or strategic partnership rather than a straight financing
• Shares issued under warrants or commitments that existed before the anti-dilution provision was signed

Beyond the carve-outs, pushing for broad-based weighted average over narrow-based or full ratchet is the single highest-leverage ask, since it's the choice of mechanism — more than any other clause detail — that decides how expensive a future down round actually turns out to be.

Reading the clause before it matters

The best time to understand a company's anti-dilution provision is at the term sheet stage of the round that creates it, not two years later when a down round is already on the table. By then the mechanism is fixed, the negotiating leverage has moved, and the only choice left is how to structure the down round itself around a clause that's already locked in. Founders raising a priced round now, even one that looks comfortably up, are effectively setting the terms for how a future reset would play out — worth treating as seriously as the valuation number itself.

Model it before the round closes

The only way to know what a down round protection clause actually costs founders is to run the numbers against the real cap table, not the summary term. Plug the pre-round share count, the new round price, and the specific anti-dilution formula into Foundily's dilution calculator and compare full ratchet against broad-based weighted average side by side. The gap between them is usually the single biggest lever left to negotiate once the valuation itself is settled.