Pro Forma Cap Table: How to Model a Series A With a New Option Pool in Excel

A pro forma cap table shows who owns what after a financing closes, built from the current share ledger plus the new investor shares, converted SAFEs and any option pool increase. For a Series A, the pro forma cap table matters most when the term sheet asks for a pool sized as a percentage of post-money shares but created out of the pre-money. That one clause decides how much of the dilution the founders absorb. This guide walks through building the spreadsheet model step by step in Excel, with a worked example you can rebuild in about 30 rows.

As of November 2026. Figures below are dated to their sources.

Key facts

Fact	Value	Source	As of
Median Series A dilution, Q1 2025 (Carta)	17.9%	carta.com	2025-03-31
Median Series A dilution a year earlier (Carta)	20.9%	carta.com	2025-03-31
Effective pre-money in Venture Hacks option pool shuffle example	$6M	venturehacks.com	2007-04-10
Headline pre-money in Venture Hacks example	$8M	venturehacks.com	2007-04-10

What a Pro Forma Cap Table Shows at Series A

Your current cap table is a record of what has already happened. The pro forma version is a forecast of the closing. It answers the questions a term sheet leaves open: how many Series A shares the lead gets, the price per share, how many shares the SAFEs convert into, and how many new options go into the pool.

Every Series A pro forma needs five blocks:

Pre-round ledger: founder common, employee common, granted options and the unallocated pool, all on a fully diluted basis.
Convertible instruments: SAFEs and notes with their caps, discounts and conversion mechanics.
Round terms: pre-money valuation, investment amount and the target pool percentage.
Solved outputs: price per share, new investor shares and new pool shares.
Post-round ownership: each holder's share count and fully diluted percentage.

Benchmarks help you check the output. Carta's Q1 2025 State of Private Markets report put median Series A dilution at 17.9%, down from 20.9% a year earlier. Carta's 2025 year-in-review said median dilution across seed through Series C rounds fell from about 18% to 16%. Carta's Series A guide puts the median option pool at 15% of fully diluted equity when a company raises its Series A. If your model shows the lead taking 30% and a 25% pool, either the deal is off-market or a formula is wrong.

Before you build anything, write the five blocks down as section headers in a blank sheet. If a term sheet input has no home, you will hard-code it later and break the model.

The Option Pool Shuffle: Why Pool Placement Moves the Price

Babak Nivi named the problem on Venture Hacks on April 10, 2007, calling it the "option pool shuffle." His example used an $8M pre-money valuation, a $2M investment and a pool equal to 20% of the post-money. Because the $2M of new options came out of the pre-money, the effective pre-money valuation was $6M. The price per share dropped to $1.00, against $1.33 if the pool had been left out. When Nivi cut the pool to 10%, the effective pre-money rose to $7M and the price to about $1.17.

Long-Term Stock Exchange (LTSE) carried the same example through to an exit. At a $50M sale with the unused pool excluded, each founder collected $18.75M with the 20% pool and $19,444,446 with the 10% pool, a difference of $694,446 per founder. That is the price of agreeing to a bigger pool than your hiring plan needs.

Three term sheet phrasings drive the math:

Pre-money pool, sized on post-money: "an unallocated pool equal to 15% of the post-money fully diluted capitalization, included in the pre-money." This is the standard VC ask, and existing holders bear all of it.
Post-money pool: the pool increase happens after the round, so the new investor is diluted alongside everyone else.
Fixed share count: "an increase of 1,500,000 shares to the pool." This is the easiest to model because there is nothing to solve.

Carta's guidance on sizing is to start bottoms-up from the hiring plan, then check top-down against comparable companies. Nivi made the same argument in 2007, that a pool backed by a named list of hires is easier to defend than a round percentage.

Takeaway: build the hiring plan tab first. List every role you expect to fill in the next 18 to 24 months with a grant size in basis points. Its total is the number you take into the pool negotiation.

How to Build a Pro Forma Cap Table in Excel, Step by Step

The standard ask creates a circular problem. The pool is a percentage of post-money shares, the post-money share count depends on the price, and the price depends on how many shares are in the pre-money. You can avoid Excel's iterative calculation entirely with one algebraic step.

Step 1: Set up the inputs

B3: Pre-money valuation.
B4: Series A investment.
B5: Target unallocated pool as a % of post-money fully diluted shares.
B6: Existing unallocated pool shares.
B7: Non-pool fully diluted shares (founders, employee common, granted options, SAFE conversion shares).

Step 2: Solve the round

B9 Post-money: =B3+B4
B10 Investor %: =B4/B9
B11 Post-money fully diluted shares: =B7/(1-B10-B5)
B12 Series A price per share: =B9/B11
B13 Series A shares: =B4/B12
B14 New pool shares: =MAX(0,B5*B11-B6)

The formula in B11 works because after closing, the non-pool holders, the investor and the full pool must add up to 100%. Non-pool holders own 1 minus the investor percentage minus the pool percentage, so dividing their fixed share count by that fraction gives total post-money shares. The MAX wrapper covers the case where your existing pool already exceeds the target.

Step 3: Convert the SAFEs before Step 2

Y Combinator's post-money SAFE user guide explains that SAFE ownership is measured after all the SAFE money but before the Series A: "The safes are like their own round, which means they are diluted by the Series A (just like everyone else)." For a cap-only post-money SAFE, ownership equals the investment divided by the post-money cap. Solve the conversion shares as =Existing_FD*SAFE_pct/(1-SAFE_pct) and add them to B7. If a SAFE carries a discount, its conversion depends on the Series A price and the circularity returns. In that case, turn on iterative calculation (File, Options, Formulas) with a cap of 100 iterations, and add a check cell that flags when the result has not converged. Read the "Company Capitalization" definition in each SAFE you hold, because whether the pool increase counts in the conversion math varies by version.

Step 4: Add check cells

Post-money fully diluted percentages sum to 100.00%.
Series A shares times price equals the investment, within $1 of rounding.
Pre-money shares (post total minus Series A shares) times price equals the pre-money valuation.
The SAFE conversion price is at or below the Series A price.

Leave the check cells in plain view at the top of the sheet. When counsel sends a revised term sheet at 11pm, you want to know straight away if a change broke the model.

Worked Example: Pro Forma Cap Table for a $10M Series A at $40M Pre-Money

The numbers below are illustrative, but the pre-money sits close to market. Carta's 2025 Series A analysis reported a median pre-money of $41.2M for non-AI rounds and $57.5M for AI rounds.

Pre-round: founders hold 8,000,000 shares, granted options total 1,000,000 and the unallocated pool is 500,000, for 9,500,000 fully diluted. Seed investors put in $1.5M on post-money SAFEs at a $15M cap, which works out to 10% ownership. Conversion shares are 9,500,000 × 0.10 / 0.90 = 1,055,556, at an implied price of about $1.42.

Term sheet: $10M at $40M pre-money, with a 15% unallocated pool post-money included in the pre-money.

Post-money: $50M. Investor share: 20%.
Non-pool shares: 8,000,000 + 1,000,000 + 1,055,556 = 10,055,556.
Post-money fully diluted shares: 10,055,556 / (1 − 0.20 − 0.15) = 15,470,086.
Price per share: $50M / 15,470,086 = $3.2320.
Series A shares: 3,094,017.
Total pool: 2,320,513, so new pool shares are 1,820,513.

Holder	Shares	Fully diluted %
Founders	8,000,000	51.7%
Granted options	1,000,000	6.5%
SAFE holders	1,055,556	6.8%
Unallocated pool	2,320,513	15.0%
Series A	3,094,017	20.0%
Total	15,470,086	100.0%

The 1,820,513 new pool shares at $3.2320 are worth about $5.88M, which puts the effective pre-money at roughly $34.1M against the $40M headline. Founders go from 75.8% after the SAFEs convert to 51.7% at close.

The same deal with a post-money pool plays out differently. The price becomes $40M / 10,555,556 = $3.7895, and the lead receives 2,638,889 shares. The pool is then topped up to 15% of the final count of 14,934,641 shares. Founders finish at 53.6% instead of 51.7%, and the lead's fully diluted stake falls to 17.7%. On the founder side that gap is about 1.9 points, and investors know it, which is why the pre-money pool is the default ask.

Model both cases side by side and bring the difference to the negotiation as a dollar figure. "$5.9M of our valuation goes to a pool we'll only use 60% of" lands harder than an argument about percentages.

Common Pro Forma Cap Table Mistakes in Series A Models

Sizing the pool on pre-money shares. If the term sheet says 15% post-money, a pool of 15% of pre-money shares will come in short, and counsel will catch it in the closing documents.
Counting granted options twice. The target is usually stated as unallocated pool. Granted options belong in the non-pool block.
Leaving out promised grants. Offers already signed but not yet approved by the board usually come out of the pool. Leave them out and your available pool is overstated.
Hard-coding SAFE shares. Link them to the cap and the pre-round count so they update when the ledger changes.
Rounding too early. Use ROUNDDOWN only on final share counts, and run price per share to four decimals.
No version log. Keep a tab that records each term sheet revision, its date and the resulting price per share.

Before you send the model to the lead or to counsel, run all six checks and reconcile the fully diluted total against your Carta or Pulley ledger to the share.

Why a Ready-Made Pro Forma Cap Table Template Saves the Round

Series A term sheets usually go through several drafts, and each one changes the pool, the price or the SAFE treatment. A model with the algebraic pool solve, SAFE conversion logic, check cells and a side-by-side comparison of pre-money and post-money pools reprices each draft in seconds. Building that from a blank sheet under deal pressure is how a formula error ends up in the closing set.

The math has been settled since Nivi's 2007 post, and the market data is public: Carta's Q1 2025 figures put median Series A dilution at 17.9% with a 15% median pool. The edge comes from walking into the pool negotiation with a hiring plan, a dollar figure for the shuffle and a model the other side can audit. Start with a tested Excel template, enter your ledger, and spend your time on the terms.