How to use the Stock Cost Basis Calculator
Estimate share cost basis and the remaining basis after a partial sale of one acquisition lot.
Calculation formula
Total purchase cost basis = shares × purchase price + acquisition fees; average cost per share = total purchase basis ÷ shares.
Recommended steps
- Enter values using the units shown beside each field.
- Review whether the example assumptions match your situation.
- Run the calculator and compare the key metrics.
- Use the source data or official rates when precision matters.
Known limitations
Single tax-lot estimate using average unit cost. Tax basis and realized gains may require specific-lot or jurisdiction rules; does not handle wash sales.
Open the calculator →