About this tool
RSUs and ISOs are different asset classes despite both being labeled equity. RSUs deliver shares automatically at vest taxed as wages; ISOs grant the right to buy shares at a fixed strike, taxed only on the spread at sale. This calculator compares both over a 4-year vest using your assumptions about stock appreciation, strike discount, and salary differential, then nets each side after tax.
How it works
The ISO side assumes you exercise at FMV at grant and sell after 1 year for long-term capital-gain treatment. Strike cost is the discount percentage applied to the equity value. Salary differential captures the cash trade-off, since startups offering ISOs typically pay a lower base.
How to use the RSU vs ISO Calculator
The RSU vs ISO Calculator is a browser-based tool that runs entirely on your device. Inputs you enter never reach a server - all calculations happen client-side in JavaScript. This means:
- Privacy: nothing is logged, sent, or stored by 3Tej. Inputs disappear when you close the tab.
- Speed: results update as you type. No network round trip.
- Offline use: once the page is cached, it works without internet.
- No signup: no account, no email, no rate limits.
Step by step
- Enter your inputs in the form above. Each field is labeled with its unit (currency, percent, kg, etc.) and the expected range.
- Read the result as it updates. The number reflects the formula commonly accepted in RSU vs ISO-related calculations.
- Adjust to see sensitivity: change one input at a time and watch how the output moves. This is the fastest way to understand which variable matters most.
- Copy or screenshot the result for later reference. The page state persists for the session if your browser allows it.
When you would use this
- Quick estimates: when you need a number now and don't want to open a spreadsheet.
- Sensitivity analysis: testing how a result changes as inputs vary, before committing to a real-world decision.
- Comparison: running the same calculation with different inputs to compare options side by side.
- Learning: building intuition for how the underlying math behaves.
- Documentation: capturing a snapshot of inputs and outputs at a point in time.
The formula explained
This calculator uses the following formula:
RSU net = (Equity × growth factor)(1 - ord) + Salary differential × 4 × (1 - ord). ISO net = (Equity × growth - strike cost)(1 - ltcg).
The reason this formula works is rooted in the underlying physics, finance, or biology of the problem. Behind every calculator is a published, peer-reviewed equation or a widely accepted convention. We do not invent formulas; we apply standard ones from textbooks, government tables, professional bodies, and academic literature.
If you are curious about the math, the simplest way to verify is to plug in two known numbers and compare against a known result. The calculator should match published examples to within rounding precision.
Frequently asked questions
When are RSUs better?
At public companies with high stock prices. RSUs deliver value automatically at vest with no exercise cost, and you only owe ordinary tax on the value you actually receive.
When are ISOs better?
At early-stage startups where strike is far below FMV. The use on appreciation plus long-term capital-gain treatment can produce a much higher net than RSUs at the same headline value.
What about the salary tradeoff?
ISO-heavy startup offers usually pay a lower base. The salary differential field captures that 4-year cash gap so the comparison is apples to apples.
Risk profile?
RSUs deliver value as long as the stock has any price. ISOs are worthless if the company exits below strike, which is common at early stage.
Is the RSU vs ISO Calculator accurate?
The RSU vs ISO Calculator applies the standard formula for rsu vs iso. Accuracy is limited only by your input precision. For decisions with material consequences, use the result as a starting point and verify with a qualified professional or the relevant official source.
Is the RSU vs ISO Calculator free?
Yes. 100% free, no signup, no payment, no API key. The site is funded by display ads that appear around the tool but not inside the calculation flow.
Are my inputs saved?
No. Inputs stay in your browser tab. Closing the tab discards them. The site uses Google Analytics for traffic measurement (anonymized) but does not see what you type into the form.
Can I use the RSU vs ISO Calculator on my phone?
Yes. The tool is responsive and tested on iOS Safari, Android Chrome, and major desktop browsers. Touch targets meet Apple's 44pt and Google's 48dp minimum guidance.
How do I report a bug or suggest improvement to the RSU vs ISO Calculator?
Email hi@3tej.com with the URL of this page and a description of what you saw vs expected. We typically respond within 72 hours and update calculators when rules or formulas change.
How accurate is the RSU vs ISO Calculator?
It applies the standard formula. Accuracy is limited only by your input precision. For decisions with material consequences (taxes, medical, legal, structural), use the result as a starting point and verify with a qualified professional in the relevant field.
Is the RSU vs ISO Calculator free to use?
Yes. 100% free, no signup, no payment, no API key. The site is funded by display ads around the tool but not inside the calculation flow.
Are my inputs saved anywhere?
No. All inputs stay in your browser tab. Closing the tab discards them. The site uses Google Analytics for traffic measurement (anonymized) but the analytics never see what you type into the form.
Does the RSU vs ISO Calculator work offline?
Yes. Once the page has loaded, it works without internet. The calculation runs in JavaScript on your device.
Can I share results from the RSU vs ISO Calculator?
Take a screenshot or copy the output. The page doesn't generate shareable URLs for specific calculations - inputs stay in your browser only.
Why are the results different from another rsu vs iso tool?
Most likely: different formula assumptions, different default values, different rounding rules, or different applicable rates. Check the methodology if both tools document it. Both can be valid for different scenarios.