The number of lands you should include in a Magic: The Gathering deck varies by format and deck type, but here are some general guidelines:

• Commander (EDH) decks (100 cards):
  The commonly recommended number of lands is around 36 to 40 lands. Many players find 36 lands gives about a 50% chance to start with 3 lands in hand, but 40 lands is often advocated as a baseline to consistently hit land drops and support a typical mana curve in Commander, which often features spells costing 3 mana or more

. Some experienced players even suggest 43 lands for optimal consistency, especially in control or midrange archetypes

. The exact number can vary based on your deck's mana curve, the presence of mana ramp cards (like Sol Ring), and your play style

• 60-card decks (Standard, Modern, etc.):
  The number of lands depends on the deck archetype:

  • Aggro decks: 23-24 lands
  • Midrange decks: 24-25 lands
  • Control decks: 26 or more lands
    Adjustments are made based on mana curve and mana sources like cantrips or mana-producing creatures

• 40-card limited decks (Draft, Sealed):
  The standard number is typically 17 lands, with aggressive mono-colored decks sometimes running as few as 15 lands, and two-color decks around 16 lands

Summary for Commander decks:

Deck Type| Suggested Land Count| Notes
---|---|---
Typical Commander| 36-40 lands| 36 lands common; 40 lands recommended for consistency
Control/Midrange| 40-43 lands| Higher land count supports bigger spells and late game
Aggro Commander| Fewer lands (around 33-35)| If curve is low and lots of ramp present

The number of lands you choose should reflect your deck’s mana curve, the number of ramp spells, and your preferred play style. Testing and tuning are often necessary to find the best balance for your specific deck