This calculator helps you determine a suitable mana base for your Magic: The Gathering deck. A good mana base ensures you can cast your spells on curve and avoid mana screw or mana flood. It takes into account your deck's mana curve, color requirements, and the number of spells you want to cast on specific turns.
function calculateManaBase() {
var totalLands = parseInt(document.getElementById("totalLands").value);
var averageManaValue = parseFloat(document.getElementById("averageManaValue").value);
var turnToCast = parseInt(document.getElementById("turnToCast").value);
var swampRequirement = parseInt(document.getElementById("swampRequirement").value);
var islandRequirement = parseInt(document.getElementById("islandRequirement").value);
var mountainRequirement = parseInt(document.getElementById("mountainRequirement").value);
var forestRequirement = parseInt(document.getElementById("forestRequirement").value);
var plainsRequirement = parseInt(document.getElementById("plainsRequirement").value);
var resultDiv = document.getElementById("result");
resultDiv.innerHTML = ""; // Clear previous results
if (isNaN(totalLands) || isNaN(averageManaValue) || isNaN(turnToCast) ||
isNaN(swampRequirement) || isNaN(islandRequirement) || isNaN(mountainRequirement) ||
isNaN(forestRequirement) || isNaN(plainsRequirement) ||
totalLands < 0 || averageManaValue < 0 || turnToCast < 1 ||
swampRequirement < 0 || islandRequirement < 0 || mountainRequirement < 0 ||
forestRequirement < 0 || plainsRequirement 0) {
recommendedSwamps = Math.round((swampRequirement / totalColorRequirement) * totalLands);
recommendedIslands = Math.round((islandRequirement / totalColorRequirement) * totalLands);
recommendedMountains = Math.round((mountainRequirement / totalColorRequirement) * totalLands);
recommendedForests = Math.round((forestRequirement / totalColorRequirement) * totalLands);
recommendedPlains = Math.round((plainsRequirement / totalColorRequirement) * totalLands);
} else {
// If no specific color requirements, a rough 50/50 split for 2-color decks, or more balanced for multi-color
// This is a very rough heuristic.
var numColors = (swampRequirement > 0) + (islandRequirement > 0) + (mountainRequirement > 0) + (forestRequirement > 0) + (plainsRequirement > 0);
if (numColors > 0) {
var landsPerColor = Math.floor(totalLands / numColors);
recommendedSwamps = swampRequirement > 0 ? landsPerColor : 0;
recommendedIslands = islandRequirement > 0 ? landsPerColor : 0;
recommendedMountains = mountainRequirement > 0 ? landsPerColor : 0;
recommendedForests = forestRequirement > 0 ? landsPerColor : 0;
recommendedPlains = plainsRequirement > 0 ? landsPerColor : 0;
// Distribute remainder
var remainder = totalLands – (recommendedSwamps + recommendedIslands + recommendedMountains + recommendedForests + recommendedPlains);
if (remainder > 0) {
if (swampRequirement > 0) recommendedSwamps++; remainder–;
if (remainder > 0 && islandRequirement > 0) recommendedIslands++; remainder–;
if (remainder > 0 && mountainRequirement > 0) recommendedMountains++; remainder–;
if (remainder > 0 && forestRequirement > 0) recommendedForests++; remainder–;
if (remainder > 0 && plainsRequirement > 0) recommendedPlains++; remainder–;
}
}
}
// Ensure the sum of recommended lands doesn't exceed total lands
var sumRecommended = recommendedSwamps + recommendedIslands + recommendedMountains + recommendedForests + recommendedPlains;
if (sumRecommended > totalLands) {
// Simple adjustment: reduce from the largest categories first
var diff = sumRecommended – totalLands;
while (diff > 0) {
if (recommendedSwamps > 0 && diff > 0) { recommendedSwamps–; diff–; }
if (recommendedIslands > 0 && diff > 0) { recommendedIslands–; diff–; }
if (recommendedMountains > 0 && diff > 0) { recommendedMountains–; diff–; }
if (recommendedForests > 0 && diff > 0) { recommendedForests–; diff–; }
if (recommendedPlains > 0 && diff > 0) { recommendedPlains–; diff–; }
if (diff > 0 && numColors > 0) { // If still diff, and colors exist, reduce equally
if (recommendedSwamps > 0) recommendedSwamps–;
else if (recommendedIslands > 0) recommendedIslands–;
else if (recommendedMountains > 0) recommendedMountains–;
else if (recommendedForests > 0) recommendedForests–;
else if (recommendedPlains > 0) recommendedPlains–;
diff–; // Account for this reduction attempt
}
}
} else if (sumRecommended 0) {
if (swampRequirement > 0) { recommendedSwamps++; diff–; }
if (diff > 0 && islandRequirement > 0) { recommendedIslands++; diff–; }
if (diff > 0 && mountainRequirement > 0) { recommendedMountains++; diff–; }
if (diff > 0 && forestRequirement > 0) { recommendedForests++; diff–; }
if (diff > 0 && plainsRequirement > 0) { recommendedPlains++; diff–; }
if (diff > 0 && totalColorRequirement == 0) { // If no specific requirements, add to a balanced distribution
if (recommendedSwamps > 0) recommendedSwamps++;
else if (recommendedIslands > 0) recommendedIslands++;
else if (recommendedMountains > 0) recommendedMountains++;
else if (recommendedForests > 0) recommendedForests++;
else if (recommendedPlains > 0) recommendedPlains++;
else { // If no lands currently recommended, add one of each color if possible
if (swampRequirement == 0 && recommendedSwamps 0 && islandRequirement == 0 && recommendedIslands 0 && mountainRequirement == 0 && recommendedMountains 0 && forestRequirement == 0 && recommendedForests 0 && plainsRequirement == 0 && recommendedPlains < totalLands) recommendedPlains++;
}
diff–;
}
}
}
resultDiv.innerHTML += "
Recommended Mana Base Breakdown:
";
resultDiv.innerHTML += "Based on your inputs, here's a suggested distribution of your " + totalLands + " lands:";
resultDiv.innerHTML += "
";
if (swampRequirement > 0) {
resultDiv.innerHTML += "
Swamps: " + recommendedSwamps + "
";
}
if (islandRequirement > 0) {
resultDiv.innerHTML += "
Islands: " + recommendedIslands + "
";
}
if (mountainRequirement > 0) {
resultDiv.innerHTML += "
Mountains: " + recommendedMountains + "
";
}
if (forestRequirement > 0) {
resultDiv.innerHTML += "
Forests: " + recommendedForests + "
";
}
if (plainsRequirement > 0) {
resultDiv.innerHTML += "
Plains: " + recommendedPlains + "
";
}
resultDiv.innerHTML += "
";
var totalRecommendedLands = recommendedSwamps + recommendedIslands + recommendedMountains + recommendedForests + recommendedPlains;
resultDiv.innerHTML += "Total recommended lands: " + totalRecommendedLands + "";
if (totalRecommendedLands !== totalLands) {
resultDiv.innerHTML += "Note: The sum of recommended colored sources (" + totalRecommendedLands + ") does not exactly match your total lands (" + totalLands + "). Adjust as needed based on utility lands or specific deck needs.";
}
resultDiv.innerHTML += "Disclaimer: This is a simplified calculator. Mana base construction is complex and depends on many factors, including specific card draw probabilities, ramp spells, mana sinks, and the importance of hitting specific colors on specific turns. Always test your mana base!";
}
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