MTG Land Calculator: How Many Lands Does Your Deck Need

How to use it

Enter your deck size and how many lands you are running. The table shows the chance of having at least two, three, four, or five lands by each turn, assuming you draw normally and mulligan nothing.

Green means comfortable, at ninety percent or better. Red means you will regularly be short.

The number to watch is three lands by turn three. Most decks have something they want to cast on turn three, and missing that land drop is the most common way a game gets away from you. If that figure is below eighty percent, you are running too few lands for your curve.

Why the calculator is a hypergeometric

Your deck is a finite set of cards and you draw without putting them back. That is precisely the situation the hypergeometric distribution describes.

The alternative you sometimes see, a binomial calculation, assumes each draw is independent, which would mean shuffling every drawn card back into the deck. That model overstates your consistency, because in a real deck every land you draw makes the next one slightly less likely.

The formula for drawing exactly k lands in n cards, from a deck of N cards containing K lands:

P(X = k) = C(K, k) * C(N-K, n-k) / C(N, n)

To get “at least k”, the calculator sums the probabilities for every value below k and subtracts from one.

A practical note on the implementation: the combination numbers involved get enormous. C(99, 40) is far larger than a JavaScript number can hold exactly, so the calculator works in logarithms and exponentiates at the end. A naive version returns Infinity divided by Infinity and reports nonsense for Commander sized decks, which is a common bug in similar tools.

What actually counts as a land

The calculator only knows the number you type, so the counting rule is on you. This is where most people get a wrong answer from a correct tool.

Count fully:

• Lands that produce mana untapped
• Lands that enter tapped. They still hit your land drop, they just cost a turn of tempo, which the calculator does not model

Count as roughly half a land each:

• Cheap mana rocks and mana dorks. They produce mana, but they cost a card and usually a turn, and they can be removed. Two of them are worth about one land for consistency purposes

Do not count:

• Cards that fix colors without adding mana
• Expensive ramp, which needs lands to cast in the first place
• Cards that search your library for a land, since they consume a card to find something you already counted

So a 99 card Commander deck with 36 lands and 10 cheap ramp pieces is closer to 41 effective lands, which is why 36 works there despite looking low as a proportion.

Why the rules of thumb exist, and when they break

Two numbers get repeated everywhere. Both are reasonable defaults and both have conditions.

Seventeen lands in a forty card limited deck. This works because limited decks have a fairly predictable curve topping out around five or six mana, and because you almost always want to hit your first four land drops. Break it downward to sixteen if your curve is unusually low, upward to eighteen if you have several expensive cards or cards that need lots of mana.

Twenty-four lands in a sixty card constructed deck. The same logic scaled up. Twenty-four is roughly forty percent, which supports a curve topping out around four to five mana.

The rules break when the deck is unusual:

• Very low curves can go to twenty or twenty-two, because they stop needing lands after turn three and extra lands become dead draws
• Control decks often want twenty-six or more, because they use mana every turn into the late game and flooding matters less when you have card draw
• Decks with heavy card selection can go lower, because they can find lands when short and convert them when flooded
• Commander breaks both rules because of singleton and because the format runs long

The tool exists so you can check your own deck rather than inheriting an assumption built for somebody else’s.

Flood is a real cost

The calculator answers one half of the question. The other half is what happens when you have too many.

Every land above what you need is a card that does nothing. A deck with thirty lands in sixty cards will almost never miss a land drop, and it will lose regularly to drawing lands when it needed spells.

The practical way to balance the two:

Add lands if you are regularly stuck below three or four mana, or if you have expensive cards sitting in hand.

Cut lands if you are regularly drawing more than one land in a row late in the game with nothing to spend the mana on.

Or add mana sinks instead of cutting, which is often the better answer. A card that converts excess mana into value, such as an activated ability you can use repeatedly, makes flood survivable without reducing your consistency. Adding sinks lets you run a healthy land count and still not lose to drawing them.