Stock Average and Cost Basis Calculator
Works out your average price across several purchases.
Average cost per share
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Share sends a link that reopens these numbers. Copy details pastes the full breakdown as a list.
Total shares —
Total cost —
Gain or loss —
Gain or loss % — %
Reading this —
The formula
average cost = (Σ shares × price + fees) ÷ Σ shares
Each purchase counts by how many shares it bought, not equally. Tax rules on cost basis differ by country.
What to watch out for
For tax, check how your country treats share matching before relying on an average.
Frequently Asked Questions
How do I average down?
Add the cost of all purchases and divide by total shares. 100 at 50 and 50 at 40 averages 46.67.