Compute average cost basis from multiple purchase lots.
Explore tools that pair well with this one—loans, investing, and planning.
When you buy the same stock at different prices, your true cost per share is a weighted average of all purchases. This tool totals quantities and amounts so you get one blended buy price—handy for tracking position cost against live quotes or for reconciling with broker statements.
Average price = Σ(quantity × price per lot) / Σ(quantity).
Add a row per purchase with shares and price. The tool computes total shares and weighted average price.
Total cost (sum of quantity × price per lot) divided by total shares. All lots are weighted by size.
Include them in your per-lot price if you want a fully loaded average; the math is the same as long as costs are embedded consistently.
Adjust quantities to post-split equivalents before averaging, or enter lots as actually transacted—consistency matters.
Yes for multiple purchases at different NAVs—weighted average cost per unit works the same way.
It helps compare your basis to the current market price for quick unrealized P&L context—use the P&L calculator for charges and sale scenarios.
Use these notes to stress-test the calculator, understand what drives the result, and choose the right tool for the decision you are making.
The average-price math assumes each entered lot belongs to the same security and should be weighted only by quantity and cost. Corporate actions, taxes, and exact broker contract-note adjustments need to be normalized by you if you want a fully loaded basis.
If you buy 10 shares at 100 and later 20 shares at 80, your average is not the midpoint of 90. The second lot carries more weight, so the blended cost moves closer to 80 than 100.
Your weighted average price is mainly a bookkeeping anchor. It helps you judge break-even level and unrealized return, but it does not tell you whether the business is worth buying more of today.
Use Stock Average when your challenge is combining multiple buy lots into one cost basis. Use Stock P&L once you know that cost basis and want to estimate realized or unrealized gain after charges.
“The stock market is a device for transferring money from the impatient to the patient.”
— Warren Buffett
