SAFEノート

SAFE vs. 転換社債:創業者向け比較ガイド

SAFEと転換社債の初期段階の創業者向け比較 — 主要な条項、長所と短所、資本構成への影響、そしてそれぞれの利用時期。

Nirji Venturesリサーチ
9 min read 読む2026-07-21
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Why This Choice Matters

Before a priced equity round, most early-stage founders raise on one of two instruments: a SAFE (Simple Agreement for Future Equity) or a convertible note. Both defer the valuation conversation and convert into equity at a future round — but they behave differently on your cap table, in your investor conversations, and if things take longer than planned.

Picking the wrong instrument can cost founders 5–15% of ownership at Series A, trigger avoidable investor friction, or (in the case of notes) create a debt liability that has to be repaid if the next round slips.

The Short Answer

SAFE: Simpler, no interest, no maturity date, no debt. Best for pre-seed to seed rounds with sophisticated angel and pre-seed VC investors, especially in the US, Singapore, and India tech ecosystems.
Convertible Note: A short-term debt instrument that converts to equity. Best when investors want interest accrual, downside protection through debt seniority, or a fixed maturity date to force a priced round.

Side-by-Side Comparison

FeatureSAFEConvertible Note
Legal natureEquity contractDebt instrument
InterestNoneTypically 4–8% per year, accrues
Maturity dateNoneUsually 18–24 months
Valuation capOptional, commonCommon
DiscountOptional, common (15–25%)Common (15–25%)
Repayment obligationNoneYes, if no qualifying round
ComplexityLow (5–10 pages)Medium (15–30 pages)
Legal cost$1K–$3K$5K–$15K
Investor familiarity (US/SG)Very highVery high
Investor familiarity (IN, MENA)GrowingHigh
MFN clauseCommonRare
Pro-rata rightsSide letterSometimes built in

Key Terms Explained

Valuation Cap

The maximum valuation at which the SAFE or note converts to equity in the next priced round. If your Series A is priced at $20M post-money and the cap is $10M, early investors convert as though the round were priced at $10M — doubling their ownership relative to new investors.

Discount Rate

A percentage discount (typically 15–25%) applied to the next round's price per share. Rewards early investors for taking pre-priced-round risk. Investors usually get the better of cap or discount, not both.

Interest (Notes Only)

Accrues on the principal — say 6% per year on $500K — and converts alongside principal into equity at the next round. Interest is not a real cash outflow, but it does dilute founders further because more dollars convert.

Maturity Date (Notes Only)

The date by which the note must convert, be repaid, or be renegotiated. If a priced round hasn't happened by then, the note technically becomes due — creating renegotiation leverage for investors.

MFN (Most Favored Nation)

If you issue a later SAFE or note with better terms, existing MFN-protected investors can elect the better terms. Common in SAFEs to protect early backers as terms evolve across a rolling raise.

Pros and Cons for Founders

SAFE — Founder View

Pros

Faster to close — often 1–3 days from term sheet to signed docs
Lower legal cost, especially with Y Combinator or SeedLegals standard templates
No maturity pressure, so a slower Series A doesn't create a debt overhang
No interest, so total dilution at conversion equals principal ÷ cap
Post-money SAFEs (the current standard) make dilution math transparent

Cons

No downside protection for investors, so some pre-seed VCs still prefer notes
Less familiar to family offices, corporates, and some emerging-market angels
MFN clauses can create surprise dilution if you sweeten terms mid-raise
Post-money SAFEs dilute founders more than pre-money SAFEs when stacked — always model the cap table before signing the second SAFE

Convertible Note — Founder View

Pros

Familiar to virtually every institutional investor and traditional lender
Interest and maturity give investors comfort, unlocking capital from more conservative sources
Can be senior to trade creditors in a downside scenario — useful signal for larger checks
Maturity date creates a natural deadline to close the next round

Cons

Legally a loan — creates a debt liability on the balance sheet
Interest accrual compounds dilution over time
Maturity risk: if the next round slips, investors can demand repayment, force conversion at a punitive valuation, or renegotiate
Higher legal cost and longer close timeline
Harder to run a rolling close with dozens of small checks

Impact on Your Cap Table

The single biggest founder mistake is stacking multiple SAFEs or notes with different caps and discounts without modeling the fully-diluted cap table at conversion.

Example: $2M Raised on SAFEs Before a $10M Series A

Assume: $2M in SAFEs at a $10M post-money cap, no discount, converting into a $10M Series A at $20M post-money.

SAFE holders convert as though price = $10M post-money, so they own 20% of the post-Series A company (their $2M ÷ $10M cap).
New Series A investors putting in $5M at $20M post get 25%.
Founders and existing option pool absorb the rest — usually a 40–50% total dilution across the two events, versus 30–35% if the SAFE conversion is modeled up front.

Practical Rules

1.Model the fully-diluted cap table at each new SAFE or note issuance, not just at Series A.
2.Set a target total pre-Series-A dilution (usually 20–25%) and back-solve for how much you can raise at what cap.
3.Prefer a single instrument type (all SAFEs or all notes) within a round to keep the waterfall clean.
4.Avoid mixing pre-money and post-money SAFEs — the dilution math diverges quickly.
5.Reserve 10–15% for an option pool refresh at Series A, which usually comes out of pre-money and dilutes founders further.

When to Use Which

Use a SAFE When

Raising from US, Singaporean, or seasoned Indian tech investors familiar with the instrument
Running a rolling close with multiple angels and pre-seed funds
Speed and low legal cost matter (typical for a bridge or first institutional check)
You expect the next priced round within 12–18 months

Use a Convertible Note When

Investors are family offices, corporates, or traditional lenders who prefer debt structures
You want the maturity date to enforce a fundraising timeline
The check size justifies the higher legal cost (usually $500K+ per investor)
Local jurisdiction is more comfortable with notes than SAFEs (still common in parts of Europe, MENA, and Latin America)

Common Founder Mistakes

Over-raising on SAFEs at a low cap.: A $10M cap feels fine until you raise $3M and give up 30% before Series A.
Ignoring interest accrual on notes.: 8% over 24 months on $1M is $167K of extra conversion — real dilution.
Multiple caps without a "most favored nation" reconciliation.: Creates messy waterfalls and unhappy early investors.
Skipping the fully-diluted model.: Founders often see the headline cap and miss the compound effect across instruments, option pool refresh, and preferred stack.
Assuming pre-money and post-money SAFEs behave identically.: They don't — post-money SAFEs guarantee investor ownership regardless of how much more you raise.

The Bottom Line

For most early-stage founders in Asia and the US, a post-money SAFE with a valuation cap and no discount is the cleanest instrument for a pre-seed to seed raise. Switch to a convertible note when investor preference, jurisdiction, or check size demands it — and always model the fully-diluted cap table before you sign anything.

If you're preparing an early-stage raise and want help structuring the instrument, cap, and cap-table impact, our team can walk through it with you.

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執筆者

Nirji Ventures Research

Capital Structuring Team

Nirji Venturesは、シンガポールに本社を置く戦略アドバイザリーおよびビジネスコンサルティング会社で、30カ国以上で35年以上の複合アドバイザリー経験を有しています。当社は、ビジネス変革、市場参入、ベンチャービルディング、資金調達準備を専門としています。

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よくある質問

What is the main difference between a SAFE and a convertible note?

A SAFE is an equity contract with no interest, no maturity date, and no repayment obligation. A convertible note is a debt instrument that accrues interest (typically 4-8% per year) and has a maturity date (usually 18-24 months) by which it must convert to equity or be repaid.

Which is better for early-stage founders, SAFE or convertible note?

For most pre-seed and seed rounds in the US, Singapore, and India, a post-money SAFE with a valuation cap is faster, cheaper, and creates no debt on the balance sheet. Convertible notes are better when investors are family offices or corporates that prefer debt structures, or when you want a maturity date to force a fundraising deadline.

How does a valuation cap affect dilution?

The cap sets the maximum valuation at which the SAFE or note converts. If you raise $2M on SAFEs at a $10M post-money cap and then price a Series A at $20M post-money, SAFE holders convert as though the round were priced at $10M — doubling their ownership relative to new investors.

Do convertible notes really need to be repaid?

Legally, yes — if no qualifying round happens by the maturity date, the note becomes due. In practice, investors usually renegotiate: extend the maturity, force conversion at a punitive valuation, or convert into a bridge SAFE. Repayment in cash is rare but the risk is real.

Can I mix SAFEs and convertible notes in the same round?

You can, but avoid it. Different instruments with different caps, discounts, interest rates, and maturity dates create a messy conversion waterfall at Series A and often surprise founders with more dilution than expected. Prefer a single instrument type per round.

What is the difference between pre-money and post-money SAFEs?

A post-money SAFE (the current YC standard) guarantees the investor a fixed percentage of the company at conversion, regardless of how much more is raised afterward. A pre-money SAFE gets diluted by later SAFEs. Post-money SAFEs are more investor-friendly and dilute founders more when stacked — always model the cap table before signing a second SAFE.

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