How to use a Deck of Cards instead of Dice in a D&D Game

How to Replicate D20 Dice Rolls using a Deck of Cards
(For best results, shuffle multiple decks together.)

Sometimes you just don't have dice handy, but you want to play anyway. If you have a deck of cards (or multiple decks) handy then here is what you need to do.

Remove 14 cards from each deck used. Remove three 2s, three 4s, three 6s, three 8s, and two 10s. Make separate decks using these 14 cards. They will be used for rolling d4s, d6s, etc.

To roll a d20...

• Draw Two Cards simultaneously.
• Add their values together to get a total.
• Face cards are 10s.
• Aces are 11s, unless you draw two of them...
• Two Aces (snake eyes) is a critical fail.
• A score of 20 or 21 is not a critical hit.
• If there is a joker, only then is it a critical hit. The chance of drawing a joker when drawing two cards from a 40 card deck is 1 in 20, so critical hits will still be just as common as normal d20s.
• Whenever a joker is drawn, reshuffle the deck of 40 cards.

While there are more face cards and 10s, there is still only 14 of them out of 40 cards. In a deck of 54 cards the average "roll" would end up being relatively low, but this deck has only 40 cards. Aces being 11s brings the average up a bit, as 10s and 11s are now 18 out of the 40 cards. Counting the 2 jokers, the resulting "rolls" should roughly mimic normal d20 dice rolling.

Note. Critical fails (snakes eyes) will be pretty rare. Something funny should happen, as decided by the DM.

With the 14 excess cards make decks for rolling a d4, d6, d8 and d10. For d12s use the d6 deck twice. Because the cards are all even numbers it will make damage higher on average, but the damage will also be higher for baddies so it evens out.