Average Buy Price (Cost Basis): Formula + Examples
Learn how to calculate average buy price (weighted cost basis) for multiple buys. Includes clear examples and common mistakes, plus break-even tips.
If you buy at different prices, your true entry is the weighted average cost basis.
The weighted average formula
Average buy price = Total cost / Total units
Total cost includes fees. Total units includes all buys.
Include fees (or you’re wrong)
Fees raise true cost basis. Remember exit fees for break-even.
Use:
Common mistakes
- Averaging prices instead of costs
- Ignoring fees
- Mixing units and dollar amounts