By Stack2One · Updated
The basic calculation
Add the eligible cost of your Bitcoin purchases, then divide by the total BTC acquired. If total cost is $6,000 and the purchases delivered 0.08 BTC, the average is $75,000 per BTC.
Why a simple average can be wrong
Suppose you buy 0.01 BTC at $50,000 per BTC and 0.09 BTC at $100,000. Averaging the two quoted prices produces $75,000, but most of the BTC came from the second purchase. The weighted total is $9,500 for 0.10 BTC, or $95,000 per BTC.
How fees affect the figure
If a fee is part of acquisition cost, including it may raise cost basis. If the fee is deducted in BTC, the amount received may be smaller. Exact tax treatment varies, so preserve both the platform statement and your calculation rather than combining fields destructively.
What average cost cannot tell you
Average cost does not measure risk tolerance, future return, tax due, or the quality of custody. It is a historical summary. An unrealized gain calculated from it can reverse quickly when the market moves.
Keep the source data
Do not retain only the average. Keep every purchase row so errors can be corrected and jurisdiction-specific lot methods can be applied if needed. See the purchase tracking guide for a practical field list.