In other formats, cards often need to be mana efficient in and of themselves because with less health and less opponents even a seemingly minor card can have a large effect. E.g., my keranos deck for cEDH is heavy in land destruction. There are tables in the article I linked to below that you can use, or you can use a hypergeometric distribution calculator. This could also be in the form of filtering like [[preordain]]. Let's take [[Sigarda, host of heron's]] for an example. Press question mark to learn the rest of the keyboard shortcuts, KefNOT the Controlfreak/The Nope Pope/Edric's weenie death squad. The mathy side of that is.... say you want a cheap ramp card by turn 3. EDIT: Per the other advice below mine, you want to obviously not run a million mana rocks/dorks. I always shoot for 38 lands, a few of which will be mostly for utility. play t2 ramp into t3 commander) and you won't just sit around waiting for more lands. It really depends on your meta and what your deck is doing, how much ramp you have, how many rocks you run etc etc. At worst, they start developing boards, setting up lock pieces, draw engines or even threaten to win the game (the last one is more of a cEDH thing tho). If it's three color, try to aim for about 12-15 basics, and in two color 17-20. EDHREC writer, former Commanderin’ host, and current Commander Time! Nonbasics like duals and fetches will lend to better fixing, but if a [[Blood Moon]], [[Back to Basics]], or [[Ruination]] comes up you might find yourself in a bind. Fix your manabase! Fit your ramp into your curve, preferably on its low end. For reference I think all of my decks have an average CMC less than 4, and the ones I've actually tuned to be optimal get closer to 3. What about playing your 10th land on turn 10 (less important still)? There’s a reason preconstructed Commander decks come with an average of over 37 lands! How much it matters? I need to be playing something of value every turn until I can win, including keeping mana up to respond to threats. So counter-intuitively, pushing your curve down will actually improve your late game. In this context, 4cmc ramp would take up your whole t3/4 without actually making Sigarda drop earlier (bc you'd drop her the nex turn either way), while a t2 ramp's benefits over 3cmc ramp spell are lessened because 3cmc spells like Cultivate ensure a land drop on the next turn and the said 2cmc spell doesn't make Sigarda drop faster than a 3cmc spell despite being cheaper. One of my worst cmc averages (mono-blue theft) is 4.11. If your deck has green, skew the lands in favor of forests and utilize cards like [[cultivate]] to hit your other colors. I have a wide spectrum of decks and can see clearly: the stronger the deck, the lower the curve. Then you can tweak to account for ramp/draw. But it can get as complicated as planning out how many of each type of card you want by each turn and how much mana they should cost. Adjust your totals if your accelerants allow you to hit your land requirements without making land drops. You need to deal with that, and no matter if you want to interact with them or just don't want to fall behind, you need cheap cards to cast and something to do on every turn cycle. If I'm playing a mana base with fetch lands or a lot of duals I might cut some black/red lands in a Grixis deck that is heavy blue in favor of more red/blue or black/blue lands. My most recent deck is a theme deck where I didn't pay attention to my curve while building it at all, but it still came out 3.74. Yeah it's part of building a deck whether you think about it or not. At best, they just ramp. In a three color deck I just start with an even distribution of color producers, then tune it later in the process. Dana is one of the hosts of the EDHRECast and the CMDR Central podcast. One of my decks has an average cmc of 2.19! Additionally, if there were any castable draw or filtering spells like Brainstorm available, I would cast them to hit a land if needed. Such a good answer! If you have any suggestions for other topics to cover in a future Superior Numbers leave a note in the comments below! Default is the typical green ramp and mana rocks. Using slots for turn 1/2 stuffs can leave you low on cards and low on power when turn 6/7/8 rolls around. There are extreme cases in which this is quite hard and this guideline can be ignored (lots of delve spells or expensive creatures you're cheating in), but those cases are exceptions rather than a guideline of their own.