Formula reminder
Post-money treatment solves pool shares from the post-closing target percent. Pre-money treatment adds pool shares before investor price per share, which can increase investor share count.
Cap table calculator
Option Pool Calculator
Estimate how many new option pool shares are needed to hit a target post-closing pool, and compare pre-money versus post-money pool treatment.
What this option pool calculator estimates
Founders usually need two answers: how many new option shares are required to hit a target post-closing pool, and whether that top-up is treated as pre-money or post-money. This calculator solves those educational estimates from current fully diluted shares, existing pool shares, target pool percent, pre-money valuation, and investment amount.
For post-money treatment, the target pool is solved from pool shares ÷ post-closing shares = target pool percent. For pre-money treatment, new pool shares are added before investor price per share is calculated, which can lower the price per share and increase investor shares — the classic option-pool-shuffle effect.
Worked example: 5M FD shares, 500k pool, 10% target, $10M / $2M round
Current fully diluted shares are 5,000,000 with 500,000 already in the pool. Target post-closing pool is 10%, pre-money valuation is $10,000,000, and investment is $2,000,000.
Under the site’s pre-money top-up model, about 113,636 new option shares are required so the expanded pool reaches the target after the financing math. That pre-money expansion increases the share base before price per share is set, which is why existing holders often absorb more dilution than a post-money pool label would suggest. Toggle to post-money treatment in the form to compare the alternate educational path with the same inputs.
Common mistakes
- Assuming an option pool target is calculated before the financing when the term sheet says post-closing.
- Ignoring how a pre-money pool top-up changes investor price per share.
- Treating simplified fully diluted shares as a substitute for the actual cap table or option plan.
Educational-use disclaimer: FounderMath is for educational planning only. It is not legal, tax, accounting, investment, securities, financial, or fundraising advice.
Read the explainer
For the narrative behind pre-money expansion, see Option Pool Shuffle.
Important limitation
This is simplified educational cap table math. Actual option pool treatment depends on financing documents and legal/accounting review.
Related tools
Founder Dilution Calculator · Option Pool Shuffle · Pre/Post-Money Calculator · SAFE Conversion Calculator
FAQ
What is the option pool shuffle?
It is the dilution shift that happens when investors require an option pool to be created or topped up before a financing round, which usually pushes more dilution onto existing holders under pre-money pool treatment.
What is the difference between pre-money and post-money pool treatment?
Pre-money treatment adds pool shares before investor price per share is set, which can lower price per share and increase investor shares. Post-money treatment solves the pool target against post-closing shares so dilution is shared differently in the simplified model.
Which inputs drive new option shares the most?
Target post-closing pool percent, existing pool shares, current fully diluted shares, and whether the top-up is modeled as pre-money or post-money. Investment size and pre-money valuation matter most when comparing ownership after the financing.
Is this a legal cap table or option-plan model?
No. This is a simplified educational calculator. Actual option pool sizing depends on financing documents, legal terms, share classes, and advisor review.
Should I still use the founder dilution calculator?
Yes. Use this page to estimate pool shares and treatment, then use the Founder Dilution Calculator to sanity-check how investor ownership plus pool expansion change founder percentages.
Last reviewed September 7, 2026. See Methodology and Sources.