Calculate colored sources with explicit assumptions

Frank Karsten’s work explains the importance of matching colored sources to spell requirements. A table calibrated for another format or mulligan model does not become a Commander table by multiplying its counts.

Landfiller’s colored-mana calculator uses an exact hypergeometric tail for draws without replacement. It reports the chance of seeing at least the required sources in the chosen number of cards. This is narrower than the chance of casting the spell.

A land that can produce both blue and green is one potential source of each color; it cannot produce both with a single tap. Do not give pain lands an arbitrary fractional discount.

Conditional lands, fetches with missing targets, tapped entry, and rocks with activation costs can make nominal source counts optimistic. Count them separately and review your intended turn sequence. Sol Ring does not produce colored mana.

List early spells with repeated colored pips and the commander’s cost. Test a double-blue spell on turn two separately from a double-blue spell on turn five.

Compare the current source count with one extra source and a later casting turn. A multi-color land can help several requirements, but its entry condition still matters.

For a 99-card library, seven-card opener and one draw each turn including turn one, turn two means nine cards seen. The following are exact chances of seeing at least two blue sources, with no mulligans, extra draws or ramp. This is our calculation, not a quoted Karsten table; seeing sources does not guarantee casting Counterspell.

The builder uses source allocation heuristics plus deck pip analysis when supplied. Those targets guide a budgeted land selection; they do not guarantee every spell is cast on curve.

An imported deck provides more useful cost information than a commander alone. Recheck the full list when you change the curve, commander, or mana rocks.