Is weighted average cost a tax basis?
Not necessarily. Tax rules vary and this tool does not apply tax-lot law.
Finance Calculator
Stock Average Calculator
Calculate weighted average purchase cost across multiple stock-buy lots with fees and optional market value.
Last reviewed: June 23, 2026Finance Phase 4 engine v1.0.1: debt, budget, pay, currency, exchange-rate, stock, and dividend formulas with no placeholder currency-rate fallbackDeterministic estimates
Calculator
Stock Average Calculator
The result is calculated from the values entered. Currency conversion pages may request ECB reference rates; other pages calculate locally.
No result yet. Enter assumptions and calculate to see the result, visual comparison and detailed rows.
What the Stock Average Calculator does
The calculator combines multiple purchase lots into a weighted average purchase cost.
How to use the Stock Average Calculator
Enter the assumptions, add rows where the page supports them, choose Calculate, then review the result card, detailed table, visual comparison and CSV export.
- Currency changes display unless the tool is a currency converter.
- Inputs stay in the browser except the optional ECB currency-rate request.
- Results are deterministic estimates from the values entered.
Formula or calculation method
Weighted average cost = total lot cost / total shares. Unrealized return = (market value - total cost) / total cost x 100.
Variables
Each lot includes shares, purchase price and fees. Current market price is optional for unrealized result context.
Assumptions
FIFO, LIFO and jurisdiction-specific tax-lot rules are not applied.
Sales are not included.
Calculation steps
Calculate each lot cost.
Sum shares, gross purchases and fees.
Divide total cost by total shares.
Compare against optional current market value.
Result interpretation
The weighted average purchase cost is a planning metric, not automatically a legal tax basis.
Worked examples
100 shares at 50 plus 10 fee and 50 shares at 40 plus 5 fee gives 150 shares, 7,015 total cost and 46.766667 weighted average cost.
Limitations
The tool excludes sales, taxes, wash sale rules, corporate actions and live quotes.
Privacy and data handling
NexaCalc does not ask for account numbers, bank credentials, saved portfolios or authentication for these tools. Currency pages may request a public ECB reference-rate file from the server-side adapter.
Financial disclaimer
This calculator provides mathematical estimates for general education and planning. It is not financial, lending, employment, tax, investment or trading advice.
Frequently asked questions
How many lots can I add?
The engine supports up to 100 purchase lots.
Is the Stock Average Calculator financial advice?
No. It is a deterministic calculator for education and planning, not financial, lending, employment, tax, investment or trading advice.
Does NexaCalc save my inputs?
No. The page does not create accounts or store debt, salary, budget, currency or stock inputs as saved plans.
Why can real-world results differ?
Actual agreements, rates, fees, dates, taxes, provider rules, payroll rules and market prices can differ from the simplified assumptions entered.
Can I export the result?
Yes. Pages with schedules or tables offer CSV export from the displayed calculation rows.
What precision does the calculator use?
The shared engine uses Decimal.js for financial math and rounds values only for display and export.
Are taxes included?
No. Phase 4 intentionally excludes income tax, capital-gains tax, withholding tax and jurisdiction-specific deductions.
References
- Consumer Financial Protection Bureau, consumer finance and debt education source family. Source.
- European Central Bank, euro foreign exchange reference rates. Source.
- Investor.gov, investor education and calculator source family. Source.
- U.S. Securities and Exchange Commission, investor resources. Source.
- U.S. Bureau of Labor Statistics, wages and compensation public data source family. Source.
Finance Phase 4 references and formula families reviewed on June 23, 2026.
Financial disclaimer
This calculator provides mathematical estimates for general education and planning. It is not financial, lending, employment, tax, investment or trading advice.
Stock prices, fees and dividends can change. Results do not include tax and are not a recommendation to buy, hold or sell an investment.