Finance & Money
Stock Average Calculator
Combine two stock purchase lots into an exact share-weighted average cost. Review lot-level quantity and cost, total shares, total position cost, and the resulting per-share basis while keeping tax-lot and corporate-action limitations visible.
Average price$111.67
Total shares15
Total cost$1,675.00
Decision view
Weighted purchase-lot basis
Combined weighted basis$111.67 per share
| Quantity | Current inputs | Formula | Current result | Decision use |
|---|---|---|---|---|
| First lot cost | — | first shares × first price | — | Component of combined basis |
| Combined shares | — | first shares + second shares | — | Average-cost denominator |
| Average price | — | total cost ÷ total shares | — | Blended acquisition price |
How to use Stock Average Calculator
- Enter the executed share count and price for the first purchase lot.
- Enter the share count and price for the second lot; use zero shares when a second lot should be excluded.
- Review total shares and total cost before relying on the combined average price.
- Use the weighted lot view to confirm that the larger share lot has the larger influence on the reported basis.
Calculator guide
Understanding Stock Average Calculator
Average cost basis combines purchases made at different prices into one per-share figure. The weighted result is more useful than a simple average because each purchase contributes according to its number of shares.
Calculation method
How the calculation works
Stock Average Calculator calculation Multiply each lot price by its share quantity, add the lot costs, add the share quantities, and divide total cost by total shares. This weights larger lots more heavily than smaller lots.
Cost-basis logic
Average price must be weighted by shares
A simple average of two quoted prices is correct only when the two purchase lots contain the same number of shares.
Worked situations
Practical examples
- Average 10 shares bought at $120 with 5 shares bought at $95.
- Compare a true share-weighted result with a simple average of the two prices.
- Test how a much larger second purchase changes combined basis.
Better inputs
Useful tips
- Use executed prices and actual share quantities from the trade confirmations.
- Include commissions in the lot cost when they form part of your tax basis.
- Keep records for every lot because tax-lot selection can differ from the overall average.
Before relying on the result
Limitations and common mistakes
- The displayed average may not match tax basis rules for every country or account type.
- Corporate actions, reinvested dividends, wash-sale adjustments, and currency effects require additional records.
- An average basis does not indicate whether adding to a position is financially appropriate.
Reference
Key terms
- Lot
- A group of shares acquired in one transaction or at one basis.
- Basis
- The recorded acquisition cost used for gain or loss calculations.
- Weighted
- Adjusted for the quantity represented by each observation.
- Break-even
- The price at which proceeds approximately equal cost before other charges.
Important note
Calculated from the entered values and stated financial terms. It is not a product quote, lending decision, tax filing, or investment recommendation.
Frequently asked questions
Why is a weighted average used?
A larger share lot represents more invested capital and therefore must contribute more to the combined average cost.
Is average cost the same as a simple average of prices?
Only when every purchase contains the same number of shares. Otherwise the quantities must be used as weights.
Does the calculator include commissions?
Not unless you incorporate them into the entered lot costs. Follow the basis rules that apply to your records.
Is the average price my guaranteed break-even price?
No. Selling fees, taxes, spreads, and currency effects can move the actual break-even level.