SAFE Note Dilution Calculator
Stack multiple SAFEs at different valuation caps and discount rates, then model how they all convert into a priced round. See the actual dilution from SAFE conversion before you sign.
Outstanding SAFEs
Priced Round (Conversion Trigger)
Conversion Details
| SAFE | Investment | Conv. Price | Shares | Ownership |
|---|---|---|---|---|
| SAFE 1 | $250K | $0.5000 | 500,000 | 4.8% |
| SAFE 2 | $500K | $0.8000 | 625,000 | 5.9% |
After SAFE Conversion + Priced Round
Founder Ownership
69.2%
SAFE Investors
7.8%
New Investors
23.1%
Total SAFE $
$750K
Post-Money
$20.0M
Pre-Money vs Post-Money SAFEs
Post-Money SAFE (YC Standard)
- Valuation cap represents the post-money valuation
- Investor gets a guaranteed ownership percentage at conversion
- $500K investment on $5M post-money cap = guaranteed 10% ownership
- Each additional SAFE directly dilutes founders, not other SAFE holders
- Simpler to model but more expensive for founders when stacking multiple SAFEs
Pre-Money SAFE (Legacy)
- Valuation cap represents the pre-money valuation
- Investor ownership depends on total money raised
- $500K on $5M pre-money cap = ownership depends on round size
- Multiple SAFE holders dilute each other, not just founders
- Harder to model but can be better for founders when raising from multiple sources
Convertible Notes and Interest Accrual
Unlike SAFEs, convertible notes are debt instruments that accrue interest. A $500,000 convertible note at 5% annual interest held for 24 months becomes $550,000 at conversion. That extra $50,000 converts into equity along with the principal, increasing total dilution beyond what founders typically calculate.
Worked Example
Principal
$500,000
Interest (5% x 24 months)
$50,000
Amount Converting
$550,000
Convertible notes also have maturity dates. If the note matures without a qualified financing event, the investor can demand repayment of the principal plus accrued interest. This creates pressure to raise a priced round or renegotiate terms before maturity, which can weaken the founder's negotiating position.
Common SAFE Stacking Mistakes
Raising too many SAFEs at low caps
Four SAFEs at $4M caps totaling $1.5M means investors collectively own 37.5% before the priced round even starts. Add Series A dilution on top and founders can drop below 40% combined ownership.
Not modeling conversion before the priced round
Founders negotiate Series A terms without accounting for outstanding SAFE conversion. The $20M pre-money looks great until 4 SAFEs convert and the effective founder dilution is 15 percentage points higher than expected.
Ignoring the MFN clause impact
A Most Favored Nation clause lets early SAFE holders adopt better terms from later SAFEs. If you give a later investor a lower cap, every MFN holder gets that cap too, significantly increasing total dilution.
Mixing pre-money and post-money SAFEs
Pre-money and post-money SAFEs convert differently. Mixing them makes the math significantly more complex and can lead to unexpected ownership outcomes. Pick one type and stick with it.