SAFE Conversion Calculator

A SAFE, short for Simple Agreement for Future Equity, is a contract in which an investor hands a company money today in exchange for the right to receive shares later, usually when the company sells preferred stock in a priced financing. Y Combinator introduced the instrument in 2013 as a lighter alternative to the convertible note. Unlike a note, a SAFE is not a loan. It carries no interest rate, has no maturity date and creates no obligation to repay in the ordinary course of business.

Those features explain its popularity at the earliest stage. A priced equity round requires negotiating a valuation, a board structure, investor rights and a full set of financing documents, which can cost weeks and meaningful legal fees. A SAFE lets a founder accept cash after agreeing on just a few terms, typically the amount and a valuation cap, and postpone the harder valuation conversation until the company has more evidence to support it. Many investors can then sign near-identical documents, which keeps the process quick.

The price of that convenience is uncertainty about ownership. A SAFE holder does not own shares on day one, so the founders' dilution is not visible in the ledger. It remains a commitment that will become shares later, on terms fixed by the cap and any discount. A SAFE conversion calculator exists to turn that deferred commitment into a concrete number, so you can see what percentage of the company you are promising away before you sign another document.

Y Combinator published its original SAFE in 2013 with a pre-money valuation cap, and replaced it in 2018 with a post-money version, which is now the form most founders encounter. The difference lies in what the cap is measured against. In a pre-money SAFE, the cap applies to the company's capitalization before the SAFE money and any other SAFEs convert. That makes each investor's percentage depend on how many other SAFEs the company signs, a figure no one can know until fundraising is over.

In a post-money SAFE, the cap is measured on a capitalization that already includes all SAFEs and convertible notes that will convert in the round. The consequence is that an investor's ownership immediately before the priced round is simple division: the purchase amount over the post-money cap. A $500,000 SAFE at an $8 million post-money cap represents 6.25% of the company's capitalization, regardless of how many further SAFEs are issued. Later SAFEs dilute the founders, not the earlier SAFE investors.

That shift is deliberate, and it shapes how founders should think. With pre-money SAFEs, the issue was unpredictability for investors. With post-money SAFEs, it is a clearer, but more founder-dilutive, arrangement in which every additional dollar of SAFE capital costs the founders its full proportional stake. A calculator that handles the post-money form lets you add a new SAFE and immediately see how many points of ownership the founding team has committed, which is exactly the visibility the instrument was designed to provide.

The valuation cap is the single most misunderstood term in a SAFE. It does not state what the company is worth, it does not set a price for the company's shares today, and no one is claiming the business would sell for that amount. It sets a ceiling on the price at which the SAFE converts. If the next priced round values the company above the cap, the SAFE holder converts as if the valuation were the cap, receiving shares at a lower price than new investors pay.

Because the cap functions as a ceiling, its practical effect is a built-in discount that grows with the success of the company. If a SAFE has an $8 million post-money cap and the company later raises at a $16 million valuation, the SAFE holder's shares are priced at half the new investors' price. If the company raises at $8 million or below, the cap does not bind and the holder converts at the round price, perhaps with a discount if one was negotiated. The better the company does, the more the cap is worth to the investor.

For founders, this means the cap is the number to negotiate, since it determines the percentage granted per dollar. Each $100,000 at a $10 million post-money cap gives away 1.0% of the company, while the same amount at a $5 million cap gives away 2.0%. Many founders set a cap at the valuation they expect in a realistic next round, and some use higher caps for later SAFEs than for earlier ones, rewarding early believers with a lower cap while still raising more at a higher price.

Y Combinator publishes the post-money SAFE in several versions. One has a valuation cap and no discount. Another has a discount and no cap. A third is a most favored nation form with neither, which converts at the price paid by new investors but allows the holder to adopt better terms offered to later SAFE investors. Some company-drafted SAFEs combine a cap and a discount, in which case the holder receives the better of the two, meaning whichever produces more shares.

A discount works differently from a cap. It reduces the price by a fixed percentage regardless of valuation. With a 20% discount and a priced round at $1.46 per share, the conversion price is $1.168, so a $100,000 SAFE buys about 85,616 shares instead of the 68,493 it would buy at full price. The discount is a fixed reward for early commitment, while the cap protects the investor against a sharp rise in valuation. A calculator can compare the two and show which one applies at any given round price.

The MFN version is common when a founder wants to raise quickly without negotiating a cap, because it postpones the question. It carries its own dilution risk, however, since the holder can adopt any more favorable cap that a later SAFE investor receives. If you issue an MFN SAFE and later sign others with a low cap, the MFN holder may elect those terms. When modeling, treat an MFN SAFE as converting at the lowest cap among later SAFEs rather than assuming it converts at the round price.

The conversion price of a post-money SAFE with a cap equals the cap divided by something called the company capitalization, and this definition decides how much dilution the founders experience. In the standard YC document, company capitalization includes all shares of capital stock issued and outstanding, all shares that could be issued on exercise of outstanding options, any promised options, and the unissued option pool. It also includes all converting securities, which means every SAFE and convertible note that converts in the financing.

Two details deserve attention. First, the capitalization excludes the shares sold to new investors in the priced round, because they are not yet part of the company at the moment the cap is applied. Second, an increase to the option pool made in connection with the priced round is included only to the extent that existing promised options exceed the pre-increase unissued pool. In practice, this means a pool top-up requested by the Series A investor generally dilutes the founders and not the SAFE holders. Always confirm this in your own document, since versions differ.

For the calculator, these rules mean that you need three kinds of input before conversion can be computed: the shares and options that exist today, the total of all other SAFEs with their caps, and the price per share or valuation of the priced round. Missing a single option grant or SAFE changes the denominator and therefore every conversion price. When entering data, reconcile each figure against your signed documents rather than relying on a spreadsheet that may be out of date.

A company has 9,000,000 founder shares, 700,000 shares under issued options and 300,000 shares in an unissued pool, a total of 10,000,000 before any SAFE converts. It has signed two post-money SAFEs. Investor A put in $500,000 at an $8 million post-money cap. Investor B put in $250,000 at a $10 million post-money cap. A's stake is $500,000 divided by $8 million, or 6.25%. B's is $250,000 divided by $10 million, or 2.5%. Together they will hold 8.75% of the company capitalization.

To find the capitalization, note that the 10,000,000 existing shares must make up the remaining 91.25%. The company capitalization is therefore 10,000,000 divided by 0.9125, or 10,958,904 shares. A's SAFE price is $8 million divided by that number, which gives $0.73, so A receives 684,932 shares. B's price is $10 million divided by the same figure, or $0.9125, so B receives 273,973 shares. Before any new money, the founders hold 9,000,000 of 10,958,904 shares, or 82.1%, down from 90% by SAFEs alone.

Now the company raises a Series A of $4 million at a $16 million pre-money valuation, with the pre-money share count including the converting SAFEs. The price is $16 million divided by 10,958,904, or $1.46, and the new investors receive 2,739,726 shares. The post-round total is 13,698,630 shares. Ownership is: new investors 20.0%, founders 65.7%, option holders and pool 7.3%, Investor A 5.0% and Investor B 2.0%. Investor A paid half the Series A price and Investor B paid 62.5% of it, which are the effective discounts created by the caps.

The same SAFE behaves differently if the company raises at a lower valuation than the cap. In the cap-only form, the document converts the SAFE at whichever price gives the holder more shares: the SAFE price calculated from the cap, or the standard price paid by the new investors. If the round price is lower than the cap price, the round price wins, and the holder simply converts alongside the new investors, with no special advantage from the cap.

Suppose the earlier example had priced the Series A at a round price of about $0.60 per share instead of $1.46. Investor A's cap price is $0.73, which is higher, so A would convert at the round price and receive roughly 833,000 shares for $500,000 instead of 684,932. This is why a cap is sometimes described as downside-neutral: it protects the investor on the upside but does not prevent them from sharing in the same price as everyone else when the company disappoints.

A real calculator should therefore compare both prices and select the lower, rather than assume the cap always applies. This also prompts a useful reflection for founders. A very high cap may protect your ownership in a strong round but offers little to a SAFE investor who cares about the floor, and a very low cap rewards the investor handsomely if the company succeeds. Calibrating the cap to a realistic outcome tends to produce fewer surprises, and fewer difficult conversations, at the time of conversion.

When a post-money SAFE converts in an equity financing, the holder generally receives a shadow series of preferred stock, often called Safe Preferred Stock, rather than the exact same shares sold to new investors. It has the same rights as the new series, except that its liquidation preference per share and its conversion price equal the SAFE price rather than the round price. The purpose is to ensure the SAFE investor's preference reflects the amount they actually paid instead of a larger number.

The numbers show why that matters. In the earlier example, Investor A paid $0.73 per share, and the Series A price was $1.46. If A's shares carried a liquidation preference of $1.46 per share, A would be entitled to twice what it invested before common stockholders were paid. With the shadow series, A's preference is $0.73 per share, which totals about $500,000, exactly the purchase amount. Founders should understand this because a large stack of SAFEs becomes a stack of preferences once converted.

Preferences affect what common stockholders receive in an exit, not the ownership percentages the calculator displays. A company that sold for a modest price might return most of the proceeds to preferred holders before common holders see anything, even though the preferred holders own a minority of the shares. A conversion calculator is therefore a starting point. For decisions about exit outcomes, build a waterfall model that includes each series' preference, participation rights and seniority, and have counsel review the actual charter language.

Not every company reaches a priced round, and the SAFE contains instructions for that case. If a liquidity event such as an acquisition or initial public offering occurs before a priced equity financing, the holder is typically entitled to the greater of two amounts. One is the original purchase amount, and the other is the amount the holder would receive if the SAFE converted into common stock at the cap price immediately before the event. This protects the investor in a low-value sale while allowing participation in a high-value one.

If the company dissolves, the holder is generally entitled to be repaid the purchase amount, ranking ahead of common stockholders but behind creditors, to the extent the company has assets available. Since a SAFE is not debt, the investor has no ability to demand repayment while the company continues to operate, and there is no maturity date that triggers it. This is one of the main practical differences from a convertible note, which usually has a maturity date and interest that the company must address at the deadline.

For a founder, the consequence is that a SAFE has no built-in deadline but also provides no automatic route to a clean cap table. If years go by without a priced round, SAFEs can remain outstanding, complicating a later financing, an acquisition or a tax review. Keep a register of outstanding SAFEs, the signing date, purchase amount, cap and any side letters, and mention them proactively in diligence. A well-organized record is far preferable to explaining ambiguity to an acquirer's lawyers.

Many SAFE investors ask for a pro rata side letter. This gives them the right to participate in the priced round, or sometimes the next round, in an amount that lets them keep their percentage after the new shares are issued. It is a separate agreement from the SAFE, and it is one of the most common causes of cap tables that are more complicated than the headline terms suggest. A pro rata right is an option to invest additional money, so it does not itself change the conversion arithmetic.

Stacking SAFEs at different caps is another area where founders discover dilution late. Because each post-money SAFE converts at its own cap, the percentages add up: investors at caps of $5 million, $8 million and $12 million contributing $200,000, $400,000 and $600,000 would own 4.0%, 5.0% and 5.0% respectively, for a combined 14.0%. The founders bear all of it. If those amounts arrive over several months, the cumulative cost is easy to overlook, so many founders keep a running total of SAFE ownership next to their cash balance.

A sensible discipline is to set a target for the total amount of SAFE ownership before opening the round, for example a limit expressed as a percentage of the company, and to track every signing against it. When you approach the limit, consider whether the next dollar should come on a priced round, on a higher cap, or from internal sources. Decisions made one SAFE at a time can feel harmless, but the sum is what the Series A investor will see on the cap table.

The most frequent error is applying a post-money cap as though it were a pre-money cap, which understates the investor's stake. At a $5 million cap, a $250,000 post-money SAFE is 5.0% of company capitalization, whereas a pre-money cap with the same numbers would give roughly 4.8% before considering other SAFEs. Another common error is forgetting the unissued option pool in the capitalization, which makes the denominator too small and the SAFE price too high. A third is leaving other SAFEs out entirely.

Equally common is mixing up the SAFE price and the priced round's price per share. The SAFE price comes from the cap and the company capitalization, while the round price comes from the new investors' pre-money valuation and the pre-money share count. Using the wrong one can produce a result that looks plausible but is off by tens of thousands of shares. Cross-check by verifying that the SAFE holder's ownership immediately before the new money equals the purchase amount divided by the cap, which is an easy test of any spreadsheet.

Finally, remember that a calculator produces an estimate. The final conversion is governed by the executed SAFE documents, the financing's definitions, any side letters and the decisions of the board and counsel. Treat the output as a planning tool for understanding your commitments, not as a legal determination, and ask your lawyer to confirm the final numbers before the cap table is updated. This guide is educational and is not legal, tax or investment advice.