Startup Company Valuation & Dilution Calculator

Understanding how much your startup is worth and how each financing round impacts ownership is crucial for founders, investors, and employees. This page explains the core concepts of valuation and dilution, then provides a simple interactive calculator that lets you model typical earlystage scenarios.

1. Key Concepts

Premoney vs. Postmoney Valuation

Premoney valuation is the estimated value of the company before a new investment is added. Postmoney valuation equals premoney valuation plus the amount of new capital injected. The formula is:

Postmoney = Premoney + New Investment

Equity Dilution

When new shares are issued, existing shareholders own a smaller percentage of the total. Dilution is expressed as:

Dilution % = (New Shares Issued Total Shares After Issue) 100

Founders often protect themselves by setting a founderfriendly cap table, using mechanisms such as option pools, antidilution provisions, or staged vesting.

Option Pools

Investors typically require a reserved pool of shares (commonly 1015% of the postmoney capitalisation) for future hires. The pool is created *before* the investment in most term sheets, which means the founders ownership will be diluted by the pool size in addition to the investors stake.

Typical EarlyStage Rounds

• Preseed: Friendsandfamily, angels, or accelerator funds. Valuations often range $1$3M.
• Seed: Angel syndicates or microVCs. Valuations $3$7M.
• Series A: Institutional VCs, usually $7$15M premoney.

2. How Dilution Affects Ownership A Simple Example

Assume a startup has 1,000,000 shares outstanding (all owned by founders). An investor offers $500,000 for a 20% stake.

1. Calculate postmoney valuation:
   Postmoney = $500,000 0.20 = $2,500,000
2. Premoney valuation:
   Premoney = $2,500,000 $500,000 = $2,000,000
3. New shares issued to give 20%:
   New Shares = (Existing Shares Desired %)/(1 Desired %) = (1,000,000 0.20)/(0.80) = 250,000
4. Total shares after the round = 1,250,000. Founders now own 80% (1,000,000 / 1,250,000).

3. Use the Calculator

Enter your current share count, the amount you plan to raise, and the percentage of the company you are willing to give up. The tool will show the new cap table, the postmoney valuation, and the dilution impact.

4. Tips for Managing Dilution

• Plan the option pool early. Including it in the premoney calculation avoids a surprise secondround dilution.
• Negotiate valuation, not just %. A higher premoney valuation reduces the number of shares you need to issue.
• Consider convertible instruments. SAFE notes or convertible notes defer valuation discussion until a later priced round, but they still convert into equity and cause dilution.
• Model multiple scenarios. Use the calculator to see how a $1M raise versus a $2M raise changes your ownership.
• Protect key founders. Vesting schedules and founderonly voting rights can preserve control even as percentages fall.

5. Final Thoughts

Valuation and dilution are not merely numbers; they shape the power dynamics and future incentives within your startup. By understanding the math and using tools like the calculator above, you can negotiate smarter, allocate equity responsibly, and keep the team motivated as the company grows.