A gain on paper shrinks after basis, holding period, and bracket. Run the rough tax before you call your preparer.
Free capital gains tax calculator from Fynvorax.
Practical tip Start with round numbers from your bank or contract. You can refine decimals after the first pass.
What to enter
Have these handy before you start. Names vary by tool, but the ideas are the same.
Sale proceeds (net of selling costs if modeled)
Cost basis: purchase price plus buy fees and improvements
Holding period in months
Federal income bracket assumptions for short- and long-term rates
Quick workflow
Enter proceeds and full adjusted basis.
Set holding months to classify short- vs long-term gain.
Read estimated federal tax—confirm state and NIIT with a CPA.
Free calculator Estimate federal tax on stock and asset sales by holding period in the capital gains tax calculator.
Worked example (illustrative)
You sell stock for $50,000 with $32,000 basis after 14 months—$18,000 long-term gain might face preferential rates if thresholds are met. Sell after 8 months and the same gain is often short-term (ordinary rates). State tax and NIIT can add layers. Enter proceeds, basis, and dates in the capital gains tax calculator—not tax advice.
Common search questions
Capital gains tax calculator — short-term vs long-term rates on stocks and assets.
Long term capital gains calculator — holding period changes the federal rate bucket.
Taxable gain calculator — sale proceeds minus adjusted basis before exemptions.
Open the tool when you already have a quote, a deadline, or a what-if and need a clear number for taxes.
Situations people use it for
Rough-order tax impact before talking to a CPA
Comparing entity or filing structures at a high level
Estimating proceeds after tax on a sale or exercise
How to read the result
Treat the output as a structured estimate. Small input changes should move the result in a direction that makes sense.
Run a conservative case first. If it still works, you have margin.
Change one field at a time so you know what actually moved the number.
Save the scenario with a name you will recognize later ("2027 refi", "15-year plan").
This model assumes: Free capital gains tax calculator from Fynvorax.
Common slip-ups
Using the result as if it were a tax return (it is only a model)
Using last year's brackets for a life event that changed your situation
Ignoring state/local when only federal was modeled
Try it with your numbers
Open the Capital Gains Tax calculator, enter your case, and keep a screenshot or PDF if you will revisit the decision. Everything runs in your browser; your inputs are not sent to our servers for the math.