How much interaction does a Commander deck need?

Most answers to this give one number for the whole format, and one number can't be right for a Core deck and an Optimized deck at once. Interaction is a race against the turn the game gets decided. Both that turn and the price of losing the race change with your bracket, and this page shows what each count actually covers at each speed, computed exactly.

Interaction answers a play, removal answers a permanent

On this page, interaction means the cards that stop something as it happens: counterspells, protection that saves your board from someone else's removal, redirects, and the hate pieces that shut a strategy off before anyone tries it. Kill spells and board wipes, the cards that deal with something already on the battlefield, are a separate budget with its own page. A card that could sit in either gets counted once, in whichever budget you bought it for.

The line matters because the two budgets fail in different ways. Removal can wait for its moment, since a threat on the battlefield is still there next turn. Interaction can't wait. A Counterspell only works if it's in your hand, with two blue mana untapped, on the turn the spell it answers is cast. So the real question is narrower than “how many.” It's how often you'll be holding something when the play that decides the game arrives.

Your bracket sets the deadline

The bracket descriptions put a rough clock on each tier: Core games generally run nine or more turns, Upgraded games end a turn or two sooner, and Optimized games can end fast. Take turn 9, turn 7 and turn 5 as the three deadlines. The last one is an assumption, because “fast” comes without a number. Here is the chance of having seen at least one interaction piece by each deadline, on the play in a 99-card deck. These are exact hypergeometrics, the same math as this site's calculators:

Read across a row and the clock turns out to matter less than you'd guess. Moving the deadline from turn 9 to turn 5 costs about twelve points at eight pieces, and fewer at the high counts. Four extra turns are only four extra cards, and four cards out of 99 don't change much.

What a miss costs is the bigger lever

What really separates the brackets is what happens when you don't have an answer. At Core, the spell you couldn't stop usually means somebody's board gets ahead of yours. The game goes on, and a wipe or a kill spell can fix it later. At Optimized, the spell you couldn't stop is often the one that ends the game. So the standard you hold your deck to should rise with the bracket, and that standard moves the count further than the clock does:

Each cell is the fewest pieces that reach that standard by that turn, on the play. Shortening the clock from turn 9 to turn 5 adds one to four pieces in any row. Raising the standard from a coin flip to three games in four adds four to six in any column. That is the honest reason the count rises with pod speed. Faster games do give you fewer draws, but mostly they make a miss more expensive. A Bracket 2 deck can live with a coin flip, so about five pieces does the job. A Bracket 4 deck can't, and three games in four by turn 5 takes twelve.

The answer, by bracket

Those ranges are the second table with a standard attached: better than even by turn 9 for the lower brackets, two games in three by turn 7 for Upgraded, three in four by turn 5 for Optimized. If your table runs faster or slower than its bracket, use the turn your games are really decided on. The calculator at the bottom of this page takes any count and any turn.

Bracket 5 is left out on purpose. A cEDH deck isn't racing a turn. It's built against a known field of other decks, and the count there comes from that field. The probability on this page still applies there, but the standards don't.

Holding up mana is a tax you pay every turn

The timing question is where low counts go wrong. Passing the turn with two mana open costs you two mana of development, every turn you do it, and the counterspell only pays you back on the turns it's actually in your hand. With five pieces in the deck you've seen one by turn 5 in 45.2% of games. A player who holds mana up every turn from there is bluffing more often than not, and paying for the bluff in tempo.

Below Bracket 3 that trade usually loses, and the fix is cheaper answers rather than fewer. Pieces that cost one or two mana let you develop and still leave one up: Swan Song, Arcane Denial and Heroic Intervention all fit beside a normal turn. A three-mana answer you have to plan your whole turn around belongs in a deck that holds one most of the time, and at five pieces yours doesn't.

At twelve pieces the same habit makes sense, because by turn 5 you're holding something in 77.8% of games. That's the other half of why Optimized decks run so much more. Past a certain density, open mana stops being a bluff.

Free spells remove the tax, and the Game Changers list draws its lines through them

A spell you can cast without paying its mana cost needs no mana held up at all. Fierce Guardianship is free while you control your commander, and so is Deflecting Swat. Force of Will costs a blue card and a life instead of mana. The strongest of this kind sit on the Game Changers list: Fierce Guardianship and Force of Will are both on it, and so is Teferi's Protection. None of them can go in a Bracket 2 deck. In Bracket 3 each one takes one of your three Game Changer slots, which puts it in direct competition with your best draw engine or tutor.

Deflecting Swat, Flawless Maneuver and Force of Negation are not on the list, so the rules allow them at any bracket. Whether they belong in Bracket 2 or 3 is a live argument, and both sides have a point. One side says the list is the line, and anything it leaves out is fair. The other says a free answer changes what the whole table can safely do on its own turn, and protecting that is what the lower brackets are for. The bracket system calls itself a tool for the pregame conversation, and a free counterspell is exactly the card to mention in it.

What counts as a piece

Counterspells count at full weight when they answer what your table actually fears. Counterspell and Arcane Denial stop anything. Negate stops only noncreature spells, which covers most of what ends games at higher brackets and less of it at Core, where the threat is often a creature.

Protection is how a deck without blue fills this budget. Heroic Intervention and Flawless Maneuver answer a board wipe aimed at your creatures, and Boros Charm can do the same with one of its three modes. Protection only answers removal, though, so it counts in a deck that has a board worth protecting.

Hate pieces answer a whole strategy before it starts, like Grafdigger's Cage and Rest in Peace against graveyard decks. They count at full weight if that strategy is at your table and at zero if it isn't. Some cross bracket lines on their own: Drannith Magistrate is a Game Changer, and a land lock like Blood Moon counts as mass land denial, which rules out everything below Bracket 4.

Redirects such as Deflecting Swat answer a targeted spell or ability by pointing it somewhere else. Count them like protection, with the bonus that the removal still hits something.

One answer covers one opponent

Every number above is about holding one piece. A four-player game has three opponents, and an answer you spend on one of them is gone for the other two. Holding two by turn 7 happens in 28.2% of games at eight pieces and 49.1% at twelve. No count you'd really run covers the whole table, and it doesn't have to. Your opponents hold interaction too, and a spell that threatens everyone is one they're also motivated to stop. Your own count is for the plays aimed at you, and for the ones you're the only player able to answer.

FAQ

How much interaction should a Commander deck run?

It depends on your bracket, because the bracket sets both how early the game is decided and how much a missed answer costs. About 4 to 6 pieces suits Brackets 1 and 2, where a better than even chance of holding one by turn 9 is enough. Bracket 3 wants 7 to 9, which holds one by turn 7 in roughly two games of three. Bracket 4 wants 11 to 14, because holding something by turn 5 in three games of four takes twelve.

How many counterspells should a Bracket 3 deck have?

Count counterspells together with protection and hate pieces, since they do the same job of answering a play as it happens. Seven to nine pieces in total suits Bracket 3, and a blue deck can make most of them counterspells. Check each one against the Game Changers list first: Fierce Guardianship and Force of Will are both on it, and each one uses up one of the three Game Changer slots a Bracket 3 deck is allowed.

Is interaction the same thing as removal?

No. Removal deals with a permanent already on the battlefield, and it can wait for a good moment because the threat stays put. Interaction answers a play as it happens, like a spell on the stack or a removal spell aimed at your board, so it only works if it is in your hand with mana open at that exact moment. That timing difference is why the two are counted as separate budgets.

Are free counterspells allowed in Bracket 2?

Fierce Guardianship and Force of Will are not, because both are Game Changers and Bracket 2 allows none. Free spells that are not on the list, such as Deflecting Swat, Flawless Maneuver and Force of Negation, are allowed by the rules at any bracket. Plenty of tables still read them as a higher-bracket signal, so they are worth raising in the pregame conversation.

What counts as interaction in a deck without blue?

Protection spells, redirects and hate pieces. Heroic Intervention and Flawless Maneuver save your board from a wipe, Deflecting Swat sends a removal spell somewhere else, and Grafdigger's Cage or Rest in Peace shut graveyard strategies down before they start. They count toward the same totals as counterspells, as long as the deck has a board worth protecting or the strategy they hate is actually at your table.