Share Incentive Plan Calculator
Your employer may have granted you shares, but the real question is: what are they actually worth after vesting, once you factor in tax, growth, and the full vesting schedule?
Plan Inputs
Adjust the variables below to project your growth.
25% / year (equal each year)
Live Summary
Real-time projection based on your inputs.
Ready to Calculate
Enter your share details and click "Update Projection" to see your estimated portfolio value and tax breakdown.
Most employees don't have a clear answer to their equity value, which is where our tool, the Share Incentive Plan Calculator becomes useful and solves your problems instantly.
It helps you estimate a realistic, after-tax value quickly, so you're not just guessing but making decisions based on clearer numbers. Whether you're in a UK SIP, holding RSUs, comparing two job offers with different equity compensation, or trying to understand your ESOP, this free tool does the heavy lifting for you.
What Is a Share Incentive Plan?
A Share Incentive Plan (SIP) is a government-approved, tax-advantaged employee share scheme in the UK.
Through it, employees can acquire shares in their company either for free or by using their pre-tax salary, and if those shares are held for the required period, they can benefit from significant tax advantages under the rules and regulations set by HM Revenue and Customs.
There are four types of shares within a UK SIP:
- Free Shares — your employer gives you up to £3,600 of shares per year, completely free.
- Partnership Shares — you buy shares from your pre-tax salary, up to £1,800 per year or 10% of your salary.
- Matching Shares — your employer matches your partnership shares, up to 2 for every 1 you buy.
- Dividend Shares — dividends earned on your SIP shares are reinvested into new shares.
The most important point is this: if you hold your SIP shares for 5 years, you won’t have to pay Income Tax or National Insurance on them. This is a rule many employees are unaware of, and it can be worth thousands of pounds. Moreover, learn how a Share Incentive Plan works.
How Does This Share Incentive Plan Calculator Work?
Calculating your after-tax equity value
Enter your share type, current share price, expected annual growth, and how long you plan to hold. The SIP calculator instantly shows your projected value, estimated tax owed, and final net take-home, broken down year by year.
Under 3 years
Full income tax and NICs apply
3 to 5 years
Income tax on original value, CGT on growth
5 years or more
Completely tax-free
No other free tool online applies this logic. Most calculators treat a UK-Share Incentive Plan the same as an RSU, which gives you completely wrong numbers.
Multi-currency Support for Global Employees
Working for a US company but based in the UK? The calculator supports GBP (£), USD ($), EUR (€), and CAD (C$), so your numbers reflect your actual currency, not a rough conversion in your head.
Custom vesting schedules
Not all equity vests equally. Use the vesting schedule calculator to set your exact split, 10% in year one, 20% in year two, and so on. Most calculators force you into a standard 25% per year model. This one doesn't.
Not all equity vests in the same way. That’s why using a vesting schedule calculator helps you define your exact distribution, like 10% in the first year, 20% in the second, and so on.
Most calculators lock you into a standard 25% per year model, but tools like shareincentivesplancalculator.com give you full flexibility to create a custom schedule based on your specific situation.
Who Should Use This Tool?
UK employees in a company SIP scheme
If your employer offers an HMRC-approved Share Incentive Plan and you’re contributing to partnership shares or receiving free shares, it’s important to use a calculator before making any early withdrawal decision. The difference in tax between exiting at 3 years versus holding for 5 years can be significant.
Employees comparing two job offers
If you use a side-by-side scenario comparison feature, you can compare Job Offer A and Job Offer B at the same time.
It allows you to model different equity types, growth assumptions, and vesting periods together, so you can clearly see the after-tax outcome of both offers.
This helps you understand not just the salary, but the real long-term value, so you can decide which offer is actually better.
Anyone with RSUs, stock options, or an ESOP
The RSU calculator, stock options calculator, and ESOP calculator all work on a similar year-by-year projection model.
You enter your grant details, and the tool shows how many shares vest each year, what they could be worth based on your expected growth rate, and finally what your net value looks like after taxes.
UK SIP Tax Rules: The 5-Year Rule Explained
Why the Holding Period Changes Everything
Many employees treat SIP shares as just a bonus and withdraw them early, but that can often turn into an expensive mistake. For example, withdrawing £3,000 worth of free shares after 2 years could mean you are taxed based on the higher value, potentially leaving you with less than your original grant.
Partnership Shares: The Upfront Saving
When you buy partnership shares through pre-tax salary, you get an immediate benefit in the form of Income Tax and National Insurance savings. For a higher-rate taxpayer, investing £1,800 could result in an upfront saving of around £756—a 42% advantage.
Use the share incentive plan estimate feature to see your personal upfront savings based on your tax band. Also, understand the difference between free, partnership, and matching shares.
Why Use This Calculator Over Others?
Many online equity calculators often label themselves as “share incentive plan calculators” but in reality apply a generic RSU-based model. They don’t account for the unique United Kingdom SIP holding period rules under the framework set by HMRC.