With a post-money SAFE, each investor's percentage is fixed when you sign: investment divided by the post-money cap. Two SAFEs at $500k on a $5M cap and $250k on an $8M cap lock in 10% and 3.125%. Founders absorb that, plus the new option pool and the Series A investors, ending at about 63.7% in our example.
- Post-money SAFE ownership = investment ÷ post-money valuation cap.
- Every additional SAFE dilutes the founders, not earlier SAFE holders.
- An option pool created in the priced round usually comes out of the pre-money, so founders bear it.
- In our example founders go from 100% to about 63.7% after two SAFEs and a Series A.
- Model every SAFE before you sign the next one.
What are the starting assumptions?
| Input | Value |
|---|---|
| Founder shares | 8,000,000 (no existing option pool) |
| SAFE A | $500,000 at a $5,000,000 post-money cap |
| SAFE B | $250,000 at an $8,000,000 post-money cap |
| Series A | $3,000,000 at a $15,000,000 pre-money valuation |
| New option pool | 10% of the post-Series A company, created in the pre-money |
We use the standard YC post-money SAFE logic and ignore discounts to keep the maths visible. For how SAFEs compare with notes and priced rounds, see SAFE vs convertible note vs priced round.
Step 1: what does each SAFE lock in?
Ownership for a post-money SAFE is investment divided by the post-money cap:
- SAFE A: $500,000 ÷ $5,000,000 = 10.000%
- SAFE B: $250,000 ÷ $8,000,000 = 3.125%
Together the SAFE holders own 13.125% of the company immediately before the Series A money comes in. The founders hold the other 86.875%.
Step 2: how many shares do the SAFEs convert into?
If founders hold 8,000,000 shares and that is 86.875% of the company at conversion, the company has 8,000,000 ÷ 0.86875 = 9,208,633 shares at that point. The SAFEs receive the difference:
- SAFE A: 10% × 9,208,633 = 920,863 shares (a conversion price of about $0.543)
- SAFE B: 3.125% × 9,208,633 = 287,770 shares
Step 3: what does the Series A add?
The Series A buys $3M ÷ $18M post-money = 16.667% of the company. The investors also require a 10% option pool after the round, created before their money comes in. So founders plus SAFEs must equal 100% − 16.667% − 10% = 73.333% of the post-round company:
9,208,633 ÷ 0.73333 = 12,557,227 shares after the round. The Series A price is about $1.43 per share.
Who owns what at the end?
| Holder | Shares | Ownership |
|---|---|---|
| Founders | 8,000,000 | 63.71% |
| SAFE A | 920,863 | 7.33% |
| SAFE B | 287,770 | 2.29% |
| Option pool | 1,255,723 | 10.00% |
| Series A investors | 2,092,871 | 16.67% |
| Total | 12,557,227 | 100% |
What are the lessons?
- Each new SAFE hits founders directly. SAFE A's 10% did not shrink when SAFE B was signed. That is the point of the post-money design, and why founders should track the sum of all SAFEs.
- The pool is a founder cost. The 10% pool came out of the pre-money. See the option pool shuffle.
- Caps matter more than amounts. A low cap on a small cheque can cost more ownership than a large cheque at a fair cap. See how to choose a valuation cap.
What if SAFE B had used a lower cap?
Change one assumption: SAFE B invests $250,000 at a $4,000,000 cap instead of $8,000,000. It now locks in 6.25% instead of 3.125%.
| Holder | Original example | SAFE B at $4M cap |
|---|---|---|
| Founders | 63.71% | 61.42% |
| SAFE A | 7.33% | 7.33% |
| SAFE B | 2.29% | 4.58% |
| Option pool | 10.00% | 10.00% |
| Series A | 16.67% | 16.67% |
A small cheque at a low cap cost founders more than two percentage points. That is the main lesson of post-money SAFEs: caps compound.
How do you keep track?
- Keep a running list of every SAFE: amount, cap, discount, date.
- Recompute the total SAFE percentage after each one.
- Model the next priced round with a realistic pool and new investor percentage.
- Share the model with your lead investor early; it avoids surprises.
What about German convertible loans?
The logic is similar, but German convertible loans often accrue interest that also converts, and the cap may be defined as pre-money rather than post-money. Read your documents carefully. See can a GmbH use a SAFE?
Frequently asked questions
How do you calculate ownership for a post-money SAFE?
Divide the investment by the post-money valuation cap. $500,000 on a $5,000,000 post-money cap equals 10%.
Do later SAFEs dilute earlier SAFE holders?
Not under the post-money SAFE: each holder's percentage is fixed against the company's capitalisation before the priced round. Later SAFEs dilute the founders.
Who pays for the option pool in a Series A?
Usually the existing holders, mostly founders, because the pool is created in the pre-money valuation.
Does a SAFE discount change the calculation?
Yes. If a discount gives a lower price than the cap, the SAFE converts at the discounted round price instead, which can increase the shares issued.
Let investors find what you're building.
OBridge is an early-access discovery network for founders and investors. Post your build, share your progress, and let verified investors mark you Investable — a private, no-amount signal of interest, not an offer or a commitment.
Join the waitlist →Sources and further reading. Y Combinator, post-money SAFE and user guide; Carta data.
Educational material, not legal, tax or investment advice. Rules and figures change; confirm with qualified counsel or a tax adviser in your jurisdiction before acting. Last updated October 6, 2026.