What this calculator does
This QSBS calculator helps startup founders, early employees, angel investors, and venture capitalists estimate their potential federal tax savings under Internal Revenue Code Section 1202. The tool allows you to input your estimated stock sale value and your anticipated marginal capital gains tax rate. It then immediately calculates your estimated total benefit—the total amount of federal capital gains tax you would save by claiming the Qualified Small Business Stock (QSBS) exemption. It's built for those planning equity liquidity events, helping you visualize the massive difference between a standard taxable sale and a fully qualified 100% tax-free QSBS exit.
How the math works
The calculation model implements the straightforward mechanics of the Section 1202 capital gains exclusion. According to IRC §1202 (reported on IRS Schedule D, Form 1040), eligible taxpayers can exclude up to 100% of their capital gains from the sale of Qualified Small Business Stock from federal taxation. The statutory limitation on this exclusion is typically the greater of $10,000,000 or 10 times the adjusted basis of the stock (the original cash investment). To determine your total estimated benefit, the calculator takes the total value of your stock sale (assuming it falls within the $10M or 10x limit) and multiplies it by your projected capital gains tax rate. For the 2026 tax year, federal long-term capital gains tax rates max out at 20%, plus a potential 3.8% Net Investment Income Tax (NIIT), bringing the effective federal rate up to 23.8% (or a rounded 24%). Multiplying your total gain by this rate yields your total tax savings.
Worked example
Imagine you are an early-stage startup employee who purchased shares in a qualifying domestic C-Corporation. You invested an initial $75,000 to exercise your options early on, meeting the active business test and the 5-year holding period requirement. Fast forward to 2026, the company goes public, and you sell your shares. Because your initial investment was $75,000, your QSBS exclusion limit is the greater of $10,000,000 or $750,000 (10x basis). Thus, your limit is $10M. If your total sale value is $1,000,000, all of this gain qualifies for the 100% exclusion. If we assume a combined federal capital gains and NIIT tax rate of 24%, the math is simple:
- Primary Value (Gain): $1,000,000
- Federal Tax Rate: 24%
- Total Estimated Benefit: $1,000,000 × 0.24 = $240,000 in federal tax savings.
Frequently Asked Questions
Does the QSBS exemption apply to state taxes?
While many states conform to the federal IRC Section 1202 standard, not all do. Most notably, California does not recognize the QSBS exemption, meaning California residents will still owe state capital gains taxes (which can be up to 13.3% or more) on the sale.
What if my company is an LLC instead of a C-Corporation?
Stock issued by an LLC or S-Corporation does not qualify as QSBS at the time of issuance. However, if the LLC converts to a domestic C-Corporation, shares issued after the conversion may qualify, and the holding period begins on the conversion date.
What if I sell my shares before the 5-year holding period?
If you hold the stock for at least 6 months but less than 5 years, you cannot claim the 1202 exemption. However, under Section 1045, you can roll the proceeds over into another qualified small business stock within 60 days to defer the capital gains tax and preserve your holding period.
Disclaimer: This calculator is for educational and scenario analysis only. It does not constitute tax, legal, or investment advice. The figures and mechanics reflect 2026 statutory rules and may change. Always consult a licensed CPA or tax advisor for professional guidance regarding your specific tax situation.
Built and verified by The Core-AI Engineering Desk — last reviewed August 2026. Calibrated strictly to 2026 statutory figures.