Cost basis, current value, after-tax P/L.
Drop in the entry price, current price, and share count. We compute gross P/L, the tax bill, and what's actually left in your pocket — for long or short positions.
Built and reviewed by Stephen Omukoko Okoth
Mathematical Economist · ex-Morgan Stanley FI · Equilar
Position
The trade
Verdict
+$ 1,480
29.5% return on cost basis • After-tax: $ 1,258
Long positions earn when price rises. The after-tax line is what actually matters; never quote returns gross of tax for a real comparison.
Result
The full picture
Cost basis
$ 5,020
Entry + commissions
Current value
$ 6,500
Price move P/L
$ 1,500
Dividends
$ 0
Gross P/L
$ 1,500
Net of fees
$ 1,480
Tax owed
$ 222
After-tax P/L
$ 1,258
Common questions
What is cost basis?
What you originally paid for the position, including commissions and fees. For tax purposes, you compute capital gain or loss as proceeds minus cost basis. Multiple lots at different prices? Each lot has its own basis.
Long vs short — how does this differ?
Long positions profit when the price rises; short positions (borrowed shares sold first) profit when the price falls. The math is symmetric, but shorts have asymmetric risk: max loss is unlimited as the price can rise indefinitely. Always set a stop on shorts.
What's a wash sale?
If you sell at a loss and buy the same security (or a substantially identical one) within 30 days before or after, the IRS disallows the loss for the current year — it adds to the cost basis of the new lot. We model the simple after-tax case and flag the wash-sale risk window in the Tax-Loss Harvesting tool.
Should I include dividends?
If you held through ex-dividend dates, yes — they're part of total return. The calculator includes a dividend field; enter total dividends received during the holding period.