# What deck size is ideal?

The person I have been playing with and I both have decks of around 130 cards.
Now I know that technically you can have as many cards as you can shuffle, but is there some sort of deck size before it becomes ineffective?

• Most competitive decks I know of are around 60 cards which is the minimum in order to ensure you get the cards you need. Nov 3, 2019 at 16:16
• Maybe duplicate: boardgames.stackexchange.com/questions/179/… Nov 3, 2019 at 16:37
• Possible duplicate of Why would you want to play with a deck bigger than 60 cards in MTG?
– Joe
Nov 4, 2019 at 15:43
• I am not sure that is a good duplicate as it is asking why you might play with a bigger deck and this is asking what the optimal size is Nov 4, 2019 at 20:29
• I read the title wrongly from the Hot Network Questions, and got worried for a second...
– Snow
Nov 6, 2019 at 12:30

Yes, and the limit may surprise you: it's 60 cards, which is exactly the minimum number of cards in a deck.

Why is this so? It's very simple: some cards are more powerful than others, but (with a few exceptions such as Relentless Rats) you can only include a limited number of copies of them in your deck. Generally speaking, you want to maximize the chance you draw your most powerful card(s), and apart from including as many copies as possible (four), the only other thing you can do about this is including as few other cards as possible. That means running 60 cards, and not a single one more.

Of course, this is a general rule, and there are some exceptions (e.g. if you build a deck around Battle of Wits you'll want somewhat more than 200 cards, but not too much more) but they are few and far between. In Limited tournaments (e.g. booster drafts) the minimum deck size is 40 cards, but again the ideal deck size is equal to the minimum size, 40.

• To pick nits, if you have a Battle of Wits deck, you probably want more than 200 cards, since BoW needs 200 just in your library to win. Nov 3, 2019 at 23:47
• The other big fact is that you want the cards of a win condition to appear together. If you make a 120 card deck by putting together two 60 cards decks, each with a strong win condition, you'll often end up with half of two win conditions, and unless their win conditions work together, that doesn't equal one whole win condition. Nov 4, 2019 at 3:26
• I can't remember where I saw it, but I remember a popular sentiment being: "If there was a sorcery that cost 0 and just drew you a card, every deck would run four." Nov 4, 2019 at 18:12
• @Aetherfox Gitaxian Probe is banned in Modern & Legacy + restricted in Vintage for a reason! Nov 4, 2019 at 19:20
• And Manamorphose is a \$10 common for the same reason. Nov 5, 2019 at 14:27

The overwhelming majority of decks will want to stick with their format's prescribed minimum (60 for a normal constructed deck).

A lot of good deck-building is about managing variance. Running the smallest permissible deck:

• Increases your chance of drawing your "best" cards when you need them. Think of it this way: a 60-card deck with 4 Lightning Bolts has about 50% more playable Lightning Bolts than a 90-card deck.
• Makes prolonged "mana flood" and "mana screw" less likely.
• Improves your deck's ability to "self-correct" as you thin it out by drawing or filtering cards.

While many players have deck-building goals besides just optimal efficiency, sticking to the minimum deck size is recommended because it helps you avoid situations where your deck just doesn't work at all.

(See this answer for a discussion of when it's strategically useful to deviate.)

Outside of the mathematics of building a strong deck, also consider:

• It's easier to properly shuffle a smaller deck. You end up wasting less of your friends' time, and yours.
• Magic cards are very much not created equal, but building 60-card decks instead of your 120-card decks means you can, conceivably, build more decks from a small collection. (Outside of tournament play, it's often considered more fun and sporting to switch decks so people aren't playing against the same deck again and again and again in a single sitting.)
• Another small side benefit is that other people's decklists and tutorial resources (such as articles about mulligan strategy, optimal land counts, &c.) will make a lot more sense to you.
• "a 60-card deck with 4 Lightning Bolts has about 50% more playable Lightning Bolts than a 90-card deck" What's the math on that? Why not 50% more playable Lightning Bolts than a 120-card deck? Nov 5, 2019 at 21:03
• 50% of 4/90 is 2/90. So 50% more than 4/90 is 6/90, which is equal to 4/60. A 60 card deck with 4 bolts has a 50% greater proportion of bolts than a 90 card deck with 4 bolts. Nov 5, 2019 at 23:41

The conventional wisdom is to run exactly the minimum possible number of cards, either 40 or 60 depending on format. This is to maximize your chances of drawing your best cards. For example in current Standard one of the best cards is Oko, Thief of Crowns. For every card you add to your deck after 60, you reduce your chances of drawing an Oko in the first place.

This isn't the end of the story however. This article by Magic Hall of Famer Frank Karsten discusses a lot of the theory. The discussion after Reason 5 is especially important. Karsten created a simulation where his deck was literally just lands and generic 1-mana 1/1s or 2-mana 2/2s. This makes the 61st card exactly as good as the 60th card. He still found that a 60-card deck was superior. Why? To quote:

An intuitive explanation for this is that a smaller deck reduces variance. Suppose that you’re playing a 40-card deck with 24 Grizzly Bears and 16 Forest and that you’re drawing your opening hand. If your first card is a land, then this reduces the ratio of Grizzly Bears in your deck from 24/40 to 24/39 - a small reduction, but it does make it more likely to draw a Grizzly Bear as your next card, which eventually improves the likelihood of drawing a nice mix between creatures and lands. Now suppose that you’re playing a 41-card deck with 25 Grizzly Bear and 16 Forest. In the same situation, the ratio reduces from 24/41 to 24/40. This reduction is slightly less than with 40 cards, which eventually leads to a slightly higher chance of mana flood. An alternative way to grasp this is by thinking about extremes: If you’re playing a ten-card deck, then it is effectively impossible to get mana screwed or mana flooded, but if you’re playing a million-card deck, then a card drawn will not noticeably affect the ratios in your remaining decks, and there is no smoothing or deck thinning effect.

That said, there are reasons to go above the standard card limit. Karsten analyzes a few of them. The most important are the first two:

Reason 1: You Are Playing with Cards that Devour Your Library

Reason 2: You Want to Deck Your Opponent or Don’t Want to Lose to Decking

Another Magic Hall of Famer Reid Duke sideboards up to 66 cards with his Jund deck against UB Mill, and survives being decked because of this (see what he says about his sideboarding at about 1hr 14min in).

Edit: ever since Ikoria was released, there's a new reason to play >60 cards: you want to use Yorion, Sky Nomad as your companion. Yorion is powerful enough that many of the top decks in multiple formats have it as a companion. They're also surprisingly consistent in spite of running 80 cards in the maindeck. Interpret that however you will.

• I like the focus on variance in this answer. Adding more cards to your deck does allow you to add more super-powerful cards, but it makes it so that you have a wider variety of super-powerful cards, and won't see any particular one consistently. A good deck should have a game plan that it's trying to achieve, and the ideal deck would play exactly the same each game with no surprises. A large deck is less effective because it will play more differently from game to game, which is exactly what you don't want when you have a good, specific plan of how to win. Nov 4, 2019 at 16:31
• I remember a casual game I played once. I ran a slightly-above-standard sized deck (I don't recall the exact count, but it was something like 64, we'll just go with that). Three players (at the end, there may've been a fourth originally), one of which was running a "mill everyone else" deck. The last turn of the game involved the miller hitting both me and the other player with a significant chunk of deck-loss, leaving me with 2 cards and the other player with what would be less than 0 (whereupon he sacrificed a bunch of creatures to deal loss-of-life to the miller). I won by default. Nov 4, 2019 at 18:23
• I agree with the general sentiment in your quote from Frank, but the examples are exactly backwards. Drawing card A increases the ratio of cards B in your deck, and adding Grizzlies increases the chance of getting mana screwed, not flooded (but the point is that adding both grizzlies and lands will increase the chance of getting both flooded and screwed). Nov 5, 2019 at 10:38

Large decks can be fun. My primary deck is 1200+ unique cards. I can play it all night long without getting bored. However, this is a fun deck, not suited for serious play. It works surprisingly well in a four person free for all against other fun decks.

That said, all the advice above is correct. If you are playing to win, you generally want the smallest legal deck. But if you're more concerned about enjoying the play rather than winning the game, then go with whatever is fun. Since you are both playing with similar sized decks, neither of you is at a disadvantage for having a large deck.

As for the design of large decks, I recommend allocating a proportion of cards for different roles. For example, you might decide to dedicate 5% of your cards with ways to deal with annoying enchantments. The point is to have more than one way to deal with situations, so you aren't looking for a specific card, but for any of the cards that handle that situation.

Please take my advice with a grain of salt. While I've been playing magic for a long time, I've never been more than a casual player. But I've always had a big deck as my primary deck.

• This seems to go into aspects that are not covering the ideal deck size and what does is already covered by other answers. Nov 5, 2019 at 23:22
• Jesus, it must take at least 10 minutes to get that many cards even close to being shuffled! Nov 8, 2019 at 13:14

It is worth noting that if you are playing limited and your opponent just provided you some bad-beats with mill cards then going up to 50 or 55 cards is a valid strategy, there does exist some corner cases.