In France, capital gain and loss are calculated using the PVCT formula (Plus Values de Cession d’Actifs Numériques):

**Capital Gain = Sale Price - (Total Acquisition Cost of Portfolio x Sale Price / Total Portfolio Value)**

For example, you purchase 1 ETH for €1,500 and 1 BTC for €10,000.

The total acquisition cost of your portfolio is €11,500.

You sell your 1 ETH for €2,000. This is the sale price.

You have other assets in your cryptocurrency portfolio. The total portfolio value, including the previously mentioned ETH, is now €20,000.

So, following the formula above:

Capital Gain = 2,000 - (11,500 x 2,000 / 20,000) = €850

Losses can only be deducted from gains if they are generated in the same fiscal year.