Investing & Portfolio

Stock Average Cost Calculator

Combine two stock purchases to calculate total shares, total cost basis, and weighted average price per share.

Inputs4 editable fields
RatesUser-entered assumptions
ModelInvesting & Portfolio
Finance calculator

Enter your numbers

The defaults are sample values. Replace them with current numbers from the decision you are modeling.

Calculations run in this browser and do not transmit your entries.

$
Your estimate will appear here

Change the sample inputs to match your scenario.

The decision behind Stock Average Cost Calculator

Combine two stock purchases to calculate total shares, total cost basis, and weighted average price per share.

Treat Stock Average Cost Calculator as a conditional calculation. It shows what follows from entered values; it does not discover an appropriate return, tax rate, allocation, claiming age, or withdrawal policy.

Assumptions entered for stock average cost

Existing shares. Shares already owned. In the Stock Average Cost Calculator record, this value sets the comparison basis for Existing average price. Preserve its source and valuation date.

Existing average price. Current average cost per share. In the Stock Average Cost Calculator record, this value is interpreted alongside New shares. Preserve its source and valuation date.

New shares. Additional shares purchased. In the Stock Average Cost Calculator record, this value changes the scale of New purchase price. Preserve its source and valuation date.

New purchase price. Price per new share. In the Stock Average Cost Calculator record, this value provides the period used by Existing shares. Preserve its source and valuation date.

How Stock Average Cost Calculator transforms the inputs

Stock Average Cost: The result is calculated directly from the visible fields and user-entered assumptions.

Stock Average Cost Calculator uses the visible values only; no unstated market return, inflation rate, tax rule, benefit amount, or account limit is inserted.

Loaded scenario to audit for stock average cost

The Stock Average Cost Calculator demonstration begins with Existing shares 40 shares; Existing average price $75; New shares 10 shares; New purchase price $68. These entries test the form and calculation order; they are not current market assumptions, recommendations, or typical retirement facts.

For stock average cost, replace the demonstration as one complete set. Then vary New purchase price while holding the other Stock Average Cost Calculator entries fixed.

Interpreting the Stock Average Cost Calculator result

A precise stock average cost result still inherits uncertainty from its inputs. Present the headline with the entered rates, dates, and exclusions instead of copying it as a stand-alone forecast.

A saved stock average cost answer should retain its unit, valuation date, and modeled assumptions so it cannot be mistaken for a guaranteed or official amount.

Where the stock average cost estimate stops

Stock average cost cannot predict market prices, distributions, interest rates, defaults, liquidity, taxes, trading costs, or investor behavior. Constant returns and yields are scenario inputs, and an illustrative allocation is not a recommendation.

Reconcile Stock Average Cost Calculator with account statements, plan documents, benefit estimates, prospectuses, tax instructions, or other governing records before relying on it.

For an adjacent decision about dollar-cost averaging, open the Dollar-Cost Averaging Calculator after saving these stock average cost inputs. After documenting stock average cost, treat expense ratio cost as a separate question in the Expense Ratio Cost Calculator. The Portfolio Rebalancing Calculator is the cleaner place to test portfolio rebalancing without changing this stock average cost scenario. When portfolio allocation becomes relevant, carry only the matching assumptions into the Portfolio Allocation Calculator.

Questions about stock average cost

What should accompany a saved stock average cost result?

Keep the Stock Average Cost Calculator inputs, result date, formula scope, and the source or rationale behind each modeled percentage with the saved output.

Why preserve the original Stock Average Cost Calculator scenario?

A saved stock average cost baseline identifies whether a later difference came from New purchase price, another assumption, or an actual account or plan change.