Federal and state tax on a capital gain
What nobody else shows
Most calculators tax a gain exactly like a wage. Nine states do not. On $100,000 of wages plus a $300,000 long-term gain, South Carolina's own capital-gains deduction saves about $6,877 against treating the gain as wages, Wisconsin's saves about $6,335, Arkansas's about $5,550, Montana's stacked preferential brackets save about $4,650, and North Dakota's exclusion saves about $3,000. Missouri excludes the gain from state tax entirely. Two states run the other way: Maryland's 2% surtax above $350,000 of AGI adds about $6,000 to that same example, and Washington -- which has no tax on wages at all -- charges $1,120 on the gain through its separate excise tax on gains above its own $270,000 exemption. Enter your own numbers above to see your state's actual treatment; it is not the same formula for everyone.
What this leaves out
The Net Investment Income Tax only applies once modified AGI crosses $200,000 single or $250,000 married filing jointly, so the row above shows nothing below that. Federal AMT is not modelled, which matters most for a gain large enough to trigger it. This is arithmetic on the numbers you enter, not tax advice.