What to do with repeated cards [duplicate]
Solution 1:
You should disenchant them. You can do this in the My Collection screen. This will give you Arcane Dust, which is used to craft new cards.
Note that there is a button allowing you to instantly disenchant all the cards you don't need. That button treats golden cards separately, so don't be afraid if you like to keep them.
A small precision about disenchanting (thanks Kim Minseo) : you shouldn't use disenchanting to exchange one card for another, since it only gives you between 12.5% and 25% of the card's crafting cost, depending on its rarity.
- Common (white) cards cost 40 dust (400 for the golden version) and give 5 (50)
- Rare (blue) cost 100 (800) and give 20 (100)
- Epic (purple) cost 400 (1600) and give 100 (400)
- Legendary (orange) cost 1600 (3200) and give 400 (1600)
What is also worth noting is that sometimes, a patch may change the behavior of a card ; then, for about two weeks, disenchanting it will give its full value. Hence, you might want to only disenchant when you want to craft a specific card, and when cards are worth their full value.
Solution 2:
You can craft your extra cards into dust, which can then be used to craft into new cards.
Because you can make any number of decks with only 2 of a card (hooray, digital games!) it's a good idea to turn anything you have extras of into dust.
Disenchanting rates are as follows:
Regular (non-gold) cards:
- Common (white) disenchants into 5 dust
- Rare (blue) disenchants into 20 dust
- Epic (purple) disenchants into 100 dust
- Legendary (orange) disenchants into 400 dust
Gold cards:
- Common (white) disenchants into 50 dust
- Rare (blue) disenchants into 100 dust
- Epic (purple) disenchants into 400 dust
- Legendary (orange) disenchants into 1600 dust
When you are in the crafting interface (accessible by the 'crafting' button in My Collection) you can easily turn all your extra cards into dust. If you have extra cards, a button appears in the blank space circled (since I have no extras at the moment, I have no button).
You can find more details (including the cost of crafting cards) on the Hearthstone wiki crafting page.