Roll a D20 die and a D4 die

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D20 + D4 Dice Roller

D20 + D4 Dice Roller
Rolls a D20 die and a D4 die
Lets you roll multiple dice like 2 D20s, or 3 D20s. Add, remove or set numbers of dice to roll
Combine with other types of dice (like D18 and D22) to throw and make a custom dice roll
Roll the dice multiple times. You can choose to see only the last roll of dice
Display sum/total of the dice thrown. You can choose to see totals only

Statistics of this Dice Roller

RollD20 + D4
Total Kinds of Dice2
Total Dice2
Minimum Sum2
Maximum Sum24
Lowest Dice Face1
Highest Dice Face20
Highest Dice Face of the Smallest Die4

Probabilities of this Dice Roller

D20 + D4

Probability of getting a 1

In technical terms this is equivalent of getting atleast one 1. This is close to 0.29, about 28.75% percent.

This is calculated by multiplying all the probabilities of not getting a 1 for each dice and then subtracting the answer from 1.

1 - (19/20 x 3/4)

Probability of not getting a 1

Probability of not getting any 1 is close to 0.71, about 71.25% percent.

This is calculated by multiplying all the probabilities of not getting a 1 for each dice.

19/20 x 3/4

Probability of getting all 1's

Probability of getting all 1's is close to 0.013, about 1.25% percent.

This is calculated by multiplying together all the probabilities of getting a 1 for each dice.

1/20 x 1/4

Probability of getting 2 1s

Probability of getting 2 1's is close to 0.013, about 1.25% percent.

This is calculated by multiplying together all the probabilities of getting a 1 for each dice that has a 1.

1/20 x 1/4

Probability of getting a 4

In technical terms this is equivalent of getting atleast one 4. This is close to 0.29, about 28.75% percent.

This is calculated by multiplying all the probabilities of not getting a 4 for each dice and then subtracting the answer from 1.

1 - (19/20 x 3/4)

Probability of not getting a 4

Probability of not getting any 4 is close to 0.71, about 71.25% percent.

This is calculated by multiplying all the probabilities of not getting a 4 for each dice.

19/20 x 3/4

Probability of getting all 4's

Probability of getting all 4's is close to 0.013, about 1.25% percent.

This is calculated by multiplying together all the probabilities of getting a 4 for each dice.

1/20 x 1/4

Probability of getting 2 4s

Probability of getting 2 4's is close to 0.013, about 1.25% percent.

This is calculated by multiplying together all the probabilities of getting a 4 for each dice that has a 4.

1/20 x 1/4

Probability of getting a 5

In technical terms this is equivalent of getting atleast one 5. This is close to 0.05, about 5% percent.

This is calculated by multiplying all the probabilities of not getting a 5 for each dice and then subtracting the answer from 1.

1 - (19/20 x 4/4)

Probability of not getting a 5

Probability of not getting any 5 is close to 0.95, about 95% percent.

This is calculated by multiplying all the probabilities of not getting a 5 for each dice.

19/20 x 4/4

Probability of getting all 5's

Probability of getting all 5's is close to 0., about 0.% percent.

This is calculated by multiplying together all the probabilities of getting a 5 for each dice.

1/20 x 0/4

Probability of getting 1 5s

Probability of getting 1 5's is close to 0.05, about 5% percent.

This is calculated by multiplying together all the probabilities of getting a 5 for each dice that has a 5.

1/20

Probability of getting a 20

In technical terms this is equivalent of getting atleast one 20. This is close to 0.05, about 5% percent.

This is calculated by multiplying all the probabilities of not getting a 20 for each dice and then subtracting the answer from 1.

1 - (19/20 x 4/4)

Probability of not getting a 20

Probability of not getting any 20 is close to 0.95, about 95% percent.

This is calculated by multiplying all the probabilities of not getting a 20 for each dice.

19/20 x 4/4

Probability of getting all 20's

Probability of getting all 20's is close to 0., about 0.% percent.

This is calculated by multiplying together all the probabilities of getting a 20 for each dice.

1/20 x 0/4

Probability of getting 1 20s

Probability of getting 1 20's is close to 0.05, about 5% percent.

This is calculated by multiplying together all the probabilities of getting a 20 for each dice that has a 20.

1/20

Probability of getting all highest faces

Probability of getting all the maximum faces (a 20 and a 4) is close to 0.013, about 1.25% percent.

This is calculated by multiplying together all the probabilities of getting the maximum face for each dice.

1/20 x 1/4

Probability of getting one of a kind

Probability of getting one of a kind is close to 0.05, about 5% percent.

There are 4 ways to get one of a kind (all 1's, all 2's, all 3's or all 4's). The probability of getting all of any kind is then caclulated by adding the probability of getting all 1's, all 2's, all 3's or all 4's. Since, probabilities of getting all 1's through all 4's are the same, we can multiply them all together. So, multiplying the probability of getting all 1's by 4 will give us the probability of getting all of any kind.

    
    4 x (1/20 x 1/4)

Javascript code to create this dice roller


    // code to create a D20 + D4 dice roller

    
    // define the sets of dice to use
    // 1 set for each kind of dice
    var dice_sets = [
                [1, 20], // 1d20        
                [1, 4], // 1d4        
            ];

    var this_roll = []; // array to store the results of this roll

    for (var ds = 0; ds < dice_sets.length; ds++) {

        //loop through each dice set

        // for each dice set, determine the numbers of dice, lowest and highest side of the dice

        var numbers_of_dice = dice_sets[ds][0];     // how many dice to roll 
        var lowest = 1;                             // lowest possible side of the dice
        var highest = dice_sets[ds][1];             // highest possible side of the dice          

        for (var j = 1; j <= numbers_of_dice; j++) {

            // loop for the number of dice

            // for each dice, generate a number between lowest and highest
            var dice_face = Math.floor(Math.random() * (highest-lowest+1) + lowest);
            this_roll.push(dice_face); //store this in the array
        }


    }            
        
    // print all the generated rolls
        
    for (j = 0; j < this_roll.length; j++) {

        // loop through the inner dice array 

        //print each dice roll value followed by a space
        document.write(this_roll[j]);
        document.write(" ");

    }

    
    

    /* 

    Sample output 

    

    */