Are Fully Diluted Shares Explained: A Legal Guide for Startup Founders in Australia

When you’re building a startup in Australia, every equity decision-from how many shares you start with to how you reward staff-shapes your long‑term control and value. One phrase you’ll hear a lot in cap table discussions is “fully diluted shares”.

What does fully diluted actually mean in practice? How do you work it out, when should you use it, and which legal documents control it?

In this guide, we’ll break down fully diluted shares in plain English, highlight common traps, and outline practical steps so you can approach fundraising and equity allocations with clarity and confidence.

What Are Fully Diluted Shares?

“Fully diluted” looks at ownership as if every possible share that could exist did exist. It’s a complete “what if” view of your share capital.

Fully diluted shares include:

• Shares that have already been issued to founders, team or investors.
• Any unallocated option pool set aside for future hires.
• Outstanding options and warrants that could be exercised in the future.
• Convertible notes and other convertible instruments, as if they converted to ordinary shares.

Investors and advisors often quote ownership on a “fully diluted basis” because it reflects the realistic end state of your cap table if all equity promises, rights and instruments are honoured.

This is different from issued (or “on issue”) shares, which is the number currently registered to holders. Fully diluted adds everything that could reasonably convert or be exercised, so percentage ownership almost always shifts when you switch between these two lenses.

Why Fully Diluted Ownership Matters For Startups

For Australian founders, fully diluted figures affect several key areas:

• Negotiations and fundraising: Most term sheets express investor stakes on a fully diluted basis. It’s also how you model pre‑ and post‑money ownership.
• Co‑founder and advisor equity: When you say “you’ll have 5%”, the natural follow‑up is “5% of what?”-issued or fully diluted. Clarity upfront prevents disputes later.
• Building an option pool: Planning how an option pool will dilute founders and early investors requires a fully diluted view. It also impacts how you allocate shares in a startup from the outset.
• Exit and due diligence: Buyers analyse the fully diluted cap table to price an acquisition and to understand eventual payouts.

Put simply, fully diluted ownership helps everyone make apples‑to‑apples comparisons. It prevents misunderstandings about “how much” someone really owns once all rights are accounted for.

How To Calculate Fully Diluted Shares (With Examples)

The basic approach is to add up everything that is, and everything that realistically could become, ordinary shares.

The Simple Formula

Fully Diluted Shares = Issued Shares + Unallocated Option Pool + Outstanding Options/Warrants + Convertible Securities (as if converted)

Worked Example

Let’s say your company has:

• 1,000,000 issued ordinary shares (held by founders)
• 100,000 unallocated option pool
• 50,000 options already granted to staff and advisors
• Convertible notes that would convert into 200,000 shares at the next round

Your fully diluted number is 1,350,000 shares (1,000,000 + 100,000 + 50,000 + 200,000).

Ownership percentages on a fully diluted basis are then each holder’s shares divided by 1,350,000, rather than by the 1,000,000 currently issued.

Pre‑ and Post‑Money Considerations

When you raise capital, investors will usually ask you to “true‑up” the option pool to a certain size (for example, 10% fully diluted) before their investment. That can shift who bears dilution. Model both scenarios-pool created pre‑money vs post‑money-so you understand the trade‑offs.

How Many Shares Should You Authorise?

Founders often ask whether there’s a “right” number of shares to start with. There isn’t a legal minimum for private companies, but thinking ahead to your future rounds helps. For context, you can read about how many shares a company can have and how the starting number plays into later allocations and splits.

Documents And Decisions That Affect Dilution

Your fully diluted cap table is not just a math exercise-it sits on top of legal documents and corporate processes. Getting these foundations right reduces risk and confusion.

Shareholders Agreement

A Shareholders Agreement sets the rules for issuing new shares, pre‑emptive rights (who gets first rights to buy new shares), drag and tag rights, and how decisions are made. It’s the single most important document for managing dilution expectations among founders and early investors.

Option Plan Rules and Grants

An employee equity plan sets out vesting, exercise price, and what happens if someone leaves. The specific plan you choose-such as an Employee Share Option Plan-drives how options are granted, when they vest, and how they convert into shares (which all flow into your fully diluted totals). For background, this overview of share options is a helpful starting point.

Note: Equity plans and grants can have tax consequences for both the company and recipients (for example, under Australia’s employee share scheme rules). It’s important to obtain tax advice before you issue options or shares to staff.

Convertible Notes and SAFEs

Convertible instruments usually convert at a future financing event using a discount and/or valuation cap. Your term sheet should say whether the option pool is counted pre‑ or post‑money and whether notes convert before or with the new round. Those levers can materially change founder dilution.

Company Constitution (or Replaceable Rules)

Every company must have governing rules. You can rely on the Corporations Act’s replaceable rules, adopt a customised Company Constitution, or use a mix. A constitution isn’t strictly mandatory for every company, but a tailored one can better support startup‑specific mechanics like multiple share classes, option issues and pre‑emptive rights.

ASIC Filings and Record‑Keeping

When you issue shares or change shareholdings, you’ll usually need to update ASIC records within required timeframes (for example, lodging details of share issues or changes to members using the relevant forms). Not every equity decision is a separate “registration”, but changes to share capital and members must be recorded and reported. This overview of ASIC Form 484 explains common company detail changes founders encounter.

Step‑By‑Step: Managing Your Cap Table And Dilution

Here’s a practical workflow to set up and maintain your equity health from day one.

1. Map Your Initial Cap Table

Decide how founding equity is split and document the logic (cash contributed, IP created, time commitment). Keep the numbers simple and easy to model. If you haven’t incorporated yet, consider future investors and staff when choosing your starting number of shares and classes.

2. Adopt Your Governance Documents

Put in place your Shareholders Agreement and governing rules (constitution or replaceable rules) that align with your growth plans, pre‑emptive rights and decision‑making thresholds.

3. Create an Option Pool With Intent

Size your pool based on your hiring plan, not a random percentage. A typical early‑stage pool might be 5–15% fully diluted, but the “right” number depends on your roadmap and need to attract talent. Use your option plan rules to set vesting and leaver provisions that suit your culture.

4. Model Pre‑Money vs Post‑Money Scenarios

Before you accept a term sheet, test how various pool sizes, note conversions and discounts interact. Model the fully diluted cap table at completion so you can see exactly who owns what.

5. Keep a Live Cap Table

Maintain one source of truth that shows both issued and fully diluted numbers. Update it promptly when you grant options, issue shares, or sign convertible instruments. A disciplined cap table saves you time during due diligence.

6. Communicate Clearly

Whenever you reference a percentage, say whether it’s on an issued or fully diluted basis, and whether it’s pre‑ or post‑money. This simple habit avoids mismatched expectations.

7. Understand Capital Raising Rules

Private companies generally raise under exemptions in the Corporations Act (for example, small‑scale offerings or wholesale/sophisticated investor rules). If you’re not running a public offer, check that your approach fits an available pathway-this overview of section 708 of the Corporations Act explains common exemptions for startups.

Common Dilution Traps, Compliance Points And Tax Tips

Most dilution headaches are preventable with a bit of process and clear paperwork. Here are the areas that regularly trip founders up.

“5%” Of What?

A promise like “5% for an advisor” can mean very different things depending on the denominator. Is that 5% of issued shares today, or 5% fully diluted after the current round and option pool top‑up? Define it expressly in the agreement and show the cap table snapshot.

Unallocated Option Pool Still Dilutes

Even if some of your option pool hasn’t been granted yet, it’s still counted in the fully diluted total. That means a bigger pool reduces everyone’s percentage today, not just later when you hire.

Note Conversions Can Surprise You

Conversion discounts, valuation caps and whether notes convert pre‑ or post‑money can shift large percentages. Always model the conversion math using realistic round sizes and check how many shares those notes will actually convert into.

Share Classes and Preferences

Issuing different classes (for example, preference shares with liquidation preferences) won’t change the fully diluted count by itself, but it will change economic outcomes on exit. Make sure your cap table shows both ownership and who gets paid first.

ASIC and Board Process

Equity changes should follow your company’s processes: board approvals, member approvals if required, issuing share certificates, updating the register, and lodging necessary ASIC notifications within time limits. Stay consistent across your cap table, board minutes and legal documents.

ESOP/ESS Tax Is Its Own Workstream

Employee equity can trigger specific tax outcomes for recipients and reporting obligations for the company. The legal setup of an option plan is only one part-build in time to obtain tax advice and to educate staff on how vesting and exercise work for them.

Clarity Beats Cleanup

Most co‑founder disputes stem from incomplete paper trails or differing memories. Confirm percentages in writing, align every grant or issue with signed documents, and keep your cap table current. It’s faster to align now than to unwind later.

Don’t Forget The Basics

Your cap table sits alongside other startup essentials: the number of shares on issue, any plan to issue more, and how you document those steps. If you’re still at the setup stage, it’s worth reading through how many shares a company can issue in Australia so you’re thinking ahead to later rounds.

Key Takeaways

• Fully diluted shares show ownership as if every option, warrant and convertible security had been exercised or converted-use this lens for fundraising, option pools and exit modelling.
• Always say whether a percentage is based on issued or fully diluted numbers, and whether it’s pre‑ or post‑money-this simple habit prevents disputes.
• Your Shareholders Agreement, option plan and governing rules (constitution or replaceable rules) set the mechanics that drive dilution-get them aligned with your growth plans.
• Keep a single, live cap table that tracks both issued and fully diluted figures, and update ASIC records when you change share capital or members.
• Model note conversions and option pool top‑ups before you sign a term sheet-small drafting differences can make big percentage swings.
• Employee equity has legal and tax dimensions-put a compliant plan in place and obtain tax advice before granting options or shares to staff.

If you’d like a consultation on setting up your share structure, option plan and fully diluted cap table for your Australian startup, you can reach us at 1800 730 617 or team@sprintlaw.com.au for a free, no‑obligations chat.