IN PLAIN ENGLISH
How much a card — or all the cards you've entered a price for — is up or down on what you paid.
FULL DEFINITION
The difference between what a card is worth today and what you paid for it.
EXAMPLE
You paid £20 for a Holofoil Charizard EX now worth £21.25: 21.25 − 20 = +£1.25, which is +6.25% of what you paid.
HOW IT'S CALCULATED
Gain/Loss = value today − what you paid, where value today = copies × today's market price for the printing (see Collectible Card Value) and what you paid is the total you entered for all the copies in that row. % = Gain/Loss ÷ what you paid × 100. The totals (Paid, Worth now, Gain/Loss) add up only the cards that have both a paid value and a price today, so the three always describe the same cards. A card with no paid value, no price today, or a paid value entered in a different currency (because your portfolio currency has changed since) is left out and counted in a note — it is not converted at today's exchange rate, which would move the cost with the currency. Card gains are not part of your net worth, which only counts what things are worth.
Educational content only. It is not personal financial advice.