Equity Dilution Calculator

About this tool

Founder ownership through seed, A, B, C — dilution math the venture canon uses.

Model founder + employee ownership through funding rounds. Inputs: initial cap, round sizes, post-money valuations, option pool top-up. Free.

RT-FIN-123 · Finance & Money

⚠ Disclaimer: Estimates only. Not tax or legal advice. U.S. taxation of equity compensation — including AMT, ISO/NSO/RSU treatment, 83(b) elections, and SAFE conversions — is highly fact-specific. Consult a CPA, tax attorney, or financial planner before exercising, vesting, or selling.

Model founder ownership through funding rounds. Each round dilutes existing shareholders by (round size ÷ post-money valuation). The tool tracks founder %, option pool %, and external investor % across seed through Series C, plus the value of the founder stake at each post-money valuation.

📋 Starting position

Founder ownership at start (after option pool)

Option pool at start

💰 Seed round

Round size raised

USD

Post-money valuation

USD

🚀 Series A

Round size raised

USD

Post-money valuation

USD

🚀 Series B

Round size raised

USD

Post-money valuation

USD

🚀 Series C

Round size raised

USD

Post-money valuation

USD

📅 Research current as of 23 May 2026 · Sources: Standard post-money cap-table dilution math. Y Combinator + Carta methodology.

Rates, regulations, and lender practices change frequently — verify current figures with your provider or licensed advisor before acting.

Founder % (final)

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Option pool % (final)

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Investors % (final)

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Founder stake $ value

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Final post-money

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Total founder dilution

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Round-by-round dilution table

Round	Raised	Post-money	Dilution	Founder % after	Founder $ after

How to Use the Equity Dilution Calculator

Set starting cap table

Founder ownership at incorporation (typically 80-100% if no co-founders / advisors) minus the option pool reserved for employees (typically 10-20% at founding, expanded at each round).

Enter round size + post-money

For each fundraising round, enter the amount raised and the post-money valuation. Pre-money is post-money minus the raise. Carta data shows typical Series A is USD 4-8M raised at USD 20-40M post; Series B USD 15-30M at USD 100-200M post.

Read the dilution table

Each row shows the dilution percentage at that round (= size ÷ post-money) and the founder's resulting ownership. Typical founder dilution per round: 15-25%. Over 4 rounds, founder ownership typically drops from ~80% to ~15-25%.

Compare founder $ value to dilution

The math that matters for founders: owning 80% of USD 5M (USD 4M) vs 20% of USD 400M (USD 80M). Dilution is bad in percentage terms but typically wealth-positive in absolute terms if rounds are up-rounds at growing valuations.

Equity Dilution — The Math Every Founder Has to Internalise

The Post-Money Dilution Formula

Each funding round, the new investors buy a share of the company equal to: investment_amount ÷ post-money_valuation. If you raise USD 5M at a USD 25M post-money, investors buy 20% of the company. Existing shareholders (founders, employees, prior investors) collectively dilute from 100% to 80% — a 20% reduction in everyone's slice. This dilution is applied uniformly across all pre-existing holders unless there are special anti-dilution provisions (typical for prior preferred-stock investors but not employees or common-stock founders).

The Y Combinator standard SAFE + post-money convention has standardised this math across early-stage US startups. Y Combinator's documents and Carta's cap-table tooling both treat post-money as the operating baseline. Carta's State of Private Markets report (latest 2024 edition) shows typical Series A founder dilution of 20-25%, Series B at 18-22%, Series C at 15-20% — meaning a typical founder team starting at 70% post-seed ends up at roughly 30-35% by Series C, depending on round sequencing.

Option Pool Expansion — The Hidden Dilution

Most VC-led rounds require the option pool to be expanded BEFORE the new money goes in — meaning the dilution from option pool expansion is borne entirely by pre-existing shareholders, not by the incoming investors. This is the "option pool shuffle" that surprises first-time founders. If you have a 10% option pool at the time of a Series A, the VC will typically require you to expand to 15-20% pre-funding, diluting you by an additional 5-10pp on top of the round's investor dilution. The tool above doesn't explicitly model the option-pool-shuffle but you can adjust the starting option pool % upward to reflect post-round target.

The option pool expansion serves a real purpose: providing equity for future hires the company needs to deliver on the new investment. But it's typically the most-negotiated single item in a term sheet because the founder dilution is real. Best practice: model the pool shuffle explicitly during negotiation and push back on overly-large expansions that benefit hypothetical future hires more than current value.

"Typical Series A founder dilution: 20-25%. After 4 rounds (seed + A + B + C), a founder team starting at 80% typically ends up at 25-35%. Dilution percentage feels bad, but absolute $ value usually grows: 80% × USD 5M = USD 4M vs 25% × USD 400M = USD 100M."

Up-Round vs Flat vs Down-Round — Where Dilution Becomes Pain

Dilution is mathematically necessary when raising new capital. The question is whether the round is at a higher valuation (up-round), the same valuation (flat), or lower (down-round). Up-rounds are good for everyone — even after dilution, founder $ value typically grows. Flat rounds preserve $ value (dilution offset by no valuation lift). Down-rounds destroy founder $ value — a USD 100M valuation dropping to USD 60M while raising USD 10M means a founder owning 30% loses USD 12M of paper wealth (30% × USD 40M valuation decline), partially offset by ownership at the new round.

Carta's data shows 2022-2024 saw a dramatic increase in flat and down rounds vs 2020-2021. Founder dilution at down-rounds typically includes anti-dilution provisions (typically broad-based weighted average) that worsen the pain by triggering ratchets on prior preferred stock. This is why founders fundraise aggressively when valuations are favourable — locking in capital at high prices reduces the future dilution math.

10 Facts About Equity Dilution

Dilution formula: investment ÷ post-money valuation = new investor %. Existing holders dilute pro-rata.

Typical Series A dilution: 20-25% per Carta State of Private Markets (2024).

The "option pool shuffle" means new pool comes out of pre-round shareholders, not new investors.

YC SAFE (post-money) is the canonical US early-stage instrument. Standardised since 2018.

After 4 typical rounds (seed + A + B + C), founder ownership drops to 25-35% from 80% starting.

Carta's 2024 data shows median founder ownership at IPO is roughly 15-20% combined across co-founders.

Anti-dilution provisions (broad-based weighted average is standard) protect prior preferred investors from down-rounds.

Pro-rata rights let prior investors participate in future rounds to maintain ownership.

Carta (carta.com) is the dominant cap-table tracking platform — used by 80%+ of US venture-backed startups.

Down-rounds in 2022-2024 hit roughly 20% of US venture rounds, up from 5-8% during the 2021 boom (Carta).

Frequently Asked Questions

Equity dilution is the reduction in existing shareholders' ownership percentage when a company issues new shares. Most commonly happens when raising new capital — the new investors get shares, increasing the total share count, so existing holders' fractional ownership drops. Math: if a company has 100 shares and you own 30 (30%), then issues 25 new shares to a new investor, you now own 30 of 125 (24%) — a 20% reduction in your percentage.
Post-money = pre-money + new investment. If you raise USD 5M at a USD 20M pre-money, post-money is USD 25M. Post-money is the company's value RIGHT AFTER the new money goes in. The new investors own (investment ÷ post-money) = 5M ÷ 25M = 20%. The Y Combinator standard SAFE since 2018 is post-money-based; older SAFEs were pre-money-based and produced different dilution math, which is why post-money is now the canonical reference.
Per Carta's 2024 State of Private Markets: typical Series A founder dilution is 20-25%; Series B is 18-22%; Series C is 15-20%. Pre-seed and seed are highly variable (10-30%). Over 4 rounds (seed + A + B + C), a founder team starting at 80% typically ends up at 25-35%. The pattern is roughly the same regardless of company size — dilution percentages compound but each round's % stays similar.
A VC negotiation tactic where the option pool is required to expand BEFORE the new money goes in — meaning the expansion dilutes existing shareholders rather than the new investors. If you have a 10% pool and your Series A VC requires 20% pool, your founders dilute an extra 10pp on top of the round's investor dilution. The math: the post-money valuation is calculated as if the larger pool already existed pre-money. Mathematically savvy founders push back on overly-large pool expansions that aren't justified by realistic future hiring needs.
A clause in preferred-stock terms that protects prior investors from down-rounds. Two flavours: full-ratchet (rare, aggressive) and broad-based weighted average (standard). With weighted-average anti-dilution, the prior preferred investor's conversion price adjusts downward proportionally to the size of the down-round — effectively converting their stake to more common shares to maintain ownership. Founders bear additional dilution from this ratchet. This is why down-rounds are particularly painful for founders.
Mostly no, IF rounds are up-rounds. Owning 25% of USD 400M (USD 100M) is dramatically better than owning 80% of USD 5M (USD 4M). The Sequoia / a16z framing: dilution is the cost of acquiring capital that grows the pie faster. The exception: if you're forced into down-rounds where dilution happens at lower valuations than prior rounds — that destroys real $ value. Anti-dilution provisions on prior preferred can compound this pain. Manage the cap table aggressively in up-rounds; defend it aggressively in challenging market conditions.
10-15% at founding, expanding to 15-20% at Series A, 15-20% at Series B (refresh), 10-15% at Series C. Total pool typically converges to 18-25% by Series C / pre-IPO across the life of the company. The total pool is sized to cover anticipated key-employee equity grants over the next 12-24 months. Companies grant 0.1-1% per employee depending on seniority and timing — early engineers and execs can receive 1-3%; later hires receive 0.05-0.5%.
A right granted to prior investors to participate in future rounds in proportion to their current ownership — preventing their stake from being diluted. If a Series A investor owns 20% and Series B is USD 10M, the pro-rata investor can buy USD 2M of the Series B to maintain 20%. Y Combinator + major US VCs all negotiate pro-rata rights aggressively. Founders should also negotiate pro-rata participation rights for their own holdings — though this is less common and harder to enforce because founders typically can't write the cheques to participate.
Math is universal but typical round sizes and valuations differ. ASEAN seed: USD 200K-1M at USD 3-8M post-money. Series A: USD 3-7M at USD 15-30M post-money — roughly 50-60% of US benchmarks. Founder dilution percentages are similar to US (20-25% Series A) but absolute values are smaller. Many Singapore-based startups deliberately use Delaware C-corp structures (with Singapore subsidiary) specifically to access US-style funding rounds with US-style terms — this combines US-investor familiarity with Singapore operational base.
Delaware C-corp parent + ASEAN operating subsidiary is the canonical structure for ASEAN startups raising from US VCs. The parent issues equity to investors and employees on US standard terms (SAFE, NVCA Series Seed/A docs). The ASEAN sub holds operations, IP, employees. Funds flow from parent to sub via intercompany loans or capital contributions. This structure also positions the company for US IPO or US acquisition exit — the most common positive-outcome paths for venture-backed startups. Carta supports this structure natively; most ASEAN founders set this up before or during their seed round.