Convertible Notes Explained: A Guide for Startup Founders

First, What Is a Convertible Note?

A convertible note is a loan from an investor that converts into equity at your next funding round. An investor gives you cash now. Instead of being repaid the loan in cash, they get shares in your company later. The price they pay for those shares is determined by the terms of the note and the valuation of your next round.

The entire purpose of a note is to raise money quickly by deferring the difficult conversation about your startup's valuation. If you don't have the metrics for a priced equity round, a note lets you get capital in the bank and start building.

The Core Mechanics: Cap, Discount, Interest, and Maturity

These four terms define how the note works. The valuation cap and discount are the most heavily negotiated.

The Valuation Cap

The valuation cap sets the maximum price your note investors will pay for their equity. They are "capped" at this valuation, protecting them if your company's value skyrockets. This is their primary reward for taking a risk on you when nobody else would.

Typical pre-seed/seed terms: $5M - $15M · Founder goal: As high as realistically possible. A low cap causes excessive dilution. · Investor goal: As low as realistically possible. A lower cap means they get more equity for their money.

The Discount Rate

The discount is a more straightforward reward. It gives the investor a percentage discount on the share price paid by the new investors in your next round.

Typical terms: 15% - 25% (20% is most common). · How it works: If your Series A investors pay $4.00 per share and your note has a 20% discount, the noteholders would convert their investment at a price of $3.20 per share ($4.00 (1 - 0.20)).

The Interest Rate

Because a convertible note is legally debt, it accrues interest. This interest is almost never paid in cash. Instead, the accrued interest gets added to the principal investment and the total amount converts to equity.

Typical terms: 2% - 8% per year. Higher rates are a red flag.

The Maturity Date

This is the date the loan is due, creating a deadline to raise a priced round (a "Qualified Financing"). If you reach this date, the noteholders have a few options: extend the date, convert at the cap, or (rarely) demand cash repayment.

Cap vs. Discount: A Worked Example

Investors get the benefit of whichever term gives them a lower share price . They never get both. Let's make this concrete.

You raise $100,000 on a convertible note with a $10M valuation cap and a 20% discount . Eighteen months later, you raise a Series A at a $16M pre-money valuation . Your new investors are paying $4.00 per share .

Based on the Discount: $4.00 Series A price (1 - 0.20) = $3.20 per share . · Based on the Valuation Cap: Price = $10M Cap / Pre-Money Valuation Shares. Here, the cap price would be roughly $2.50 per share ($10M cap is 62.5% of the $16M valuation, so the price is 62.5% of $4.00).

The outcome: The investor chooses the price that gives them more shares for their money. In this case, the $2.50 price implied by the valuation cap is much better for them than the $3.20 price from the discount. They will convert their $100,000 (plus accrued interest) into stock at $2.50 per share.

The Big Debate: Convertible Notes vs. SAFEs

You cannot discuss notes without mentioning their modern, founder-friendly alternative: the SAFE (Simple Agreement for Future Equity) .

A SAFE, created by Y Combinator, is a warrant to purchase stock in a future round. It is not debt. This is the most critical difference.

The bottom line: For most early-stage tech startups in the US, the post-money SAFE has replaced the convertible note as the market standard.

Why SAFEs Won

SAFEs are simpler and remove the two most problematic features of notes:

No Maturity Date: This removes the "ticking clock" that gives investors leverage to force a conversion or renegotiate if you haven't raised a priced round by a certain deadline. A SAFE remains in place indefinitely until a conversion event. · No Interest Rate: This simplifies the math and bookkeeping. It also reinforces that a SAFE is an investment, not a loan.

The "post-money" SAFE is the current standard. It clarifies that the SAFE holders' ownership is calculated after all the SAFE money is accounted for, giving founders a precise understanding of their dilution. You should use the standard YC post-money SAFE documents, which are widely accepted.

So, When Should You Still Use a Convertible Note?

A SAFE should be your default. However, you might use a note if:

An investor requires it. Some angels, family offices, or investors outside major tech hubs are more familiar with debt instruments and may insist on a note. If it's a critical investor, it's usually not a deal-breaker. · You are raising a "bridge" round. If you're raising a small amount of money to extend your runway between two priced rounds (e.g., between Series A and B), a note is sometimes used. · You operate in a legal jurisdiction where SAFEs are not common. Outside the US, note-like instruments are often more standard.

The 4 Most Common (and Costly) Founder Mistakes

Notes are simple on the surface, but a few mistakes can have huge consequences for your cap table.

1. The Low Valuation Cap Trap

This is the biggest mistake you can make. An excessively low cap is a gift to your early investors at your expense. If you raise your seed round at a $20M valuation but your notes convert at a $5M cap, those early investors get a 75% discount, taking a much larger chunk of your company than you intended.

How to avoid it: Model the dilution. A simple rule of thumb is that your first round of notes should not sell more than 20% of your company. You can estimate this: (Amount Raised on Notes / Valuation Cap) = % Equity Sold (if cap is hit) . A $1M raise on a $5M cap is 20% dilution. A $1M raise on a $10M cap is 10%. See the difference?

2. Fumbling the Maturity Date

The maturity date is real. While investors rarely demand cash repayment (it kills the company and their investment), they can use it as a leverage point to demand better terms. If you have multiple notes with staggered maturity dates, your life becomes an administrative nightmare of seeking extensions.

How to avoid it: Raise on a single note with the same maturity date for all investors in the round. If the date is approaching and you need an extension, be proactive. Email investors 60-90 days out with an update and a clear request: '''We're making strong progress on X and Y, and plan to raise a priced round in Q4. To give us the runway to do that, we'd like to request a 6-month extension to the note's maturity date. Here is the amendment to sign.'''

3. Not Defining What Happens if You Don't Raise

What happens if your company becomes profitable and you don't need to raise a big VC round? Or what if you sell the company before raising a priced round? Your note needs to specify the outcome.

At maturity: Many notes convert automatically at the valuation cap. Be prepared for this; you will have new shareholders. · At acquisition (M&A): Most notes give the investor a choice: either get their money back (often with a multiplier, like 1.5x or 2x their investment) or convert into equity at the cap and participate in the acquisition as a shareholder.

How to avoid it: Read your documents. Make sure these scenarios are clearly defined in a way you find acceptable. A 1x payout on M&A is standard; anything over 2x is aggressive.

4. Ignoring the Interest Rate's Impact

A "low" 5% interest rate doesn't seem like much, but over 24 months it adds 10% to the converting principal. This isn't a deal-breaker, but you must account for it in your dilution models. It's another small way a note is less clean than a SAFE.

Red Flags: Predatory Note Terms to Watch For

An uncapped note: Never, ever sign a note with no valuation cap. It means your earliest investors get the same price as investors in your next round, erasing any reward for their early risk. · High interest rates: Anything above 8% is non-standard and punitive. · Excessive M&A multiples: A 1.5x or 2x payout to the investor if you sell the company is sometimes acceptable. Demands for 3x or more are not. · Aggressive discounts: A discount above 25% is not typical for a standard seed round. · "Stacking" MFN clauses: A "Most Favored Nation" clause says you must give the investor the better terms of any subsequent note. This is fair, but some bad MFNs can stack, creating a cascade a messy terms. Use standard documents to avoid this.

How to Apply This: Your Fundraising Playbook

Don't just read this; use it. Here are the immediate, actionable steps.

Decide: SAFE or Note? Start with the assumption you will use a post-money SAFE. Only deviate if a make-or-break investor for your round insists on a note. If they do, understand exactly what you're signing up for. · Use Standard Documents. Do not draft your own agreements or let an investor do it. Use the industry-standard YC SAFE documents or get convertible note templates from a reputable source like Stripe Atlas or Clerky. 99% of the terms should be boilerplate. · Model Your Dilution. Create a simple cap table spreadsheet. Build three scenarios for your next priced round: · Base Case: Series A at a valuation 2x your note cap. · Upside Case: Series A at a valuation 4x your note cap. · Downside Case: Series A at a valuation equal to your note cap. · Talk to an Experienced Startup Lawyer. Do not try to save a few thousand dollars by doing this yourself. A good lawyer will have seen hundreds of these deals. Their fee is insurance against catastrophic mistakes that can cost you millions and even kill your company down the line.