Stacked Post-Money SAFEs Protect Investors—and Dilute Founders Faster

Stacked post-money valuation-cap SAFEs protect each investor’s estimated ownership from dilution by later SAFEs, so the percentages accumulate against founders and other current stockholders. Calculate each SAFE as its purchase amount divided by its own cap, add the results, and then carry the resulting cap table through the priced round and any option-pool increase.

This is an estimate for compatible cap-only post-money SAFEs when the cap-based conversion price controls—not a closing cap table. In Y Combinator’s published example, $500,000 at a $10 million cap represents 5% and $1 million at a $16 million cap represents 6.25%, leaving 11.25% sold before the priced round. The same example explains that subsequent SAFE money dilutes current stockholders, while the priced round later dilutes founders, existing investors and SAFE holders.

Calculate each SAFE on its own terms

For each compatible valuation-cap SAFE, use the indicative formula purchase amount ÷ post-money valuation cap. Never add the investments first and divide by one selected cap: different caps buy different percentages per dollar.

The cap is also not a declaration of the startup’s present value. It helps set a conversion price under the agreement. Orrick’s dilution analysis illustrates the distinction with $1 million at a $10 million post-money cap—about 10%—and warns that several differently capped SAFE rounds can obscure the total ownership sold.

Create one worksheet row per executed instrument:

• holder and closing date;
• purchase amount and post-money cap;
• discount or MFN terms, if present;
• pro rata side letter;
• estimated cap-based percentage;
• conversion method ultimately applied.

Do not force discount-only SAFEs, uncapped MFN instruments, notes or modified forms into the amount-divided-by-cap formula. A SAFE may also convert at the financing price when that produces the contractual result.

Build ownership immediately before the priced round

Add the estimated percentages for the compatible SAFEs and call the total S. Current stockholders collectively retain 1 − S; multiply each current holder’s pre-SAFE percentage by that remainder.

Assume, conditionally, that founders held 90% and an existing employee pool held 10%. If the SAFE stack totals 20%, founders fall to 72% (90% × 80%), the pool falls to 8% (10% × 80%), and SAFE holders receive 20% collectively.

This is the investor protection—and the founder cost—behind the title. In Optimal Counsel’s two-round illustration, $2 million at a $20 million post-money cap and $3 million at a $30 million cap each correspond to 10%. Under the YC-style terms discussed there, the first SAFE group is not diluted by the later group, so current stockholders absorb the combined 20% before conversion.

Apply the priced-round dilution to every pre-round holder

Return to the YC amounts and assume founders owned 100% before the SAFEs. The estimated pre-round table is founders 88.75%, SAFE A 5% and SAFE B 6.25%.

If new investors receive 20% post-closing and there is no pool change or pro rata participation, the pre-round holders retain 80%. Multiply every pre-round percentage by 80%:

• founders: 88.75% × 80% = 71%;
• SAFE A: 5% × 80% = 4%;
• SAFE B: 6.25% × 80% = 5%;
• new investors: 20%.

SAFE holders are protected from one another before the financing, not from dilution forever. The YC post-money SAFE guide says the priced-round money and a new or increased pool adopted with that financing dilute the SAFEs. It also cautions that a sufficiently low financing price can give SAFE holders more shares than the cap-based estimate.

Model the option pool as a separate layer

Record issued options, promised awards and the unissued pool before entering the negotiated post-closing target. The distinction between existing and newly created pool equity determines which holders bear the incremental dilution.

For a simplified conditional scenario with no prior pool, suppose new investors receive 20% and a new post-closing pool receives 10%. That leaves 70% for founders and converted SAFE holders. Preserving their 88.75:5:6.25 proportions produces founders at 62.125%, SAFE A at 3.5%, SAFE B at 4.375%, new investors at 20% and the pool at 10%.

The pool therefore reduces founders from 71% in the no-pool scenario to 62.125%. Actual term sheets may instead require a top-up from an existing pool, use a different fully diluted denominator or place the increase in the pre-money capitalization; model that language with a full pre-money and post-money bridge.

Reconcile the worksheet with the signed documents

The worksheet exposes the economics but cannot determine the final share counts. YC’s page for US SAFE financing documents lists three post-money forms—valuation cap without discount, discount without cap and uncapped MFN—plus an optional pro rata side letter. Amendments and non-YC forms may produce different outcomes.

Legal review should confirm the applicable conversion price, the defined Company Capitalization, treatment of outstanding and promised awards, warrants and notes, pool increases, pro rata participation and multiple closings. The priced-round documents must establish the actual share counts and preferred-stock series. Until that reconciliation is complete, treat amount divided by cap as an ownership estimate and the stacked worksheet as a decision model.

Also read:

• Startup Option Pools: Calculate the Pre-Money Dilution Before You Sign
• Pre-Money vs Post-Money Valuation: Calculate Ownership and Option-Pool Dilution
• Smart Money Is More Than Cash: How Founders Test an Investor’s Real Value