Dice Roller

Choose the dice first, then roll. The dice on screen update as you change the settings, before you roll.

1. Set Number of dice from 1 to 30. The default is 2.
2. Choose Sides: d4, d6, d8, d10, d12, d20 or d100. A d6 shows pips like a real die, and every other die shows its number on a tile.
3. If your game adds a fixed bonus or penalty, enter it under Add a modifier, anywhere from -1000 to 1000. It is added once to the total, not to each die.
4. Press Roll the dice or press the Space bar.
5. Read the total in large type, the individual dice under it, and the note that gives the lowest, highest and average die and the possible range. The list keeps the last 12 rolls, and Clear history empties it.

For example, 1 die with d20 and a modifier of 5 is a roll of 1d20+5, which can produce any total from 6 to 25.

Each die is independent, so two six-sided dice make 6 x 6 = 36 equally likely pairs. A total of 7 can be built six ways (1 and 6, 2 and 5, 3 and 4, plus the reverse of each), so it comes up 6 times in 36, or 16.7 percent. A total of 2 or 12 needs one exact pair, so it comes up 1 time in 36, or 2.8 percent.

Three simple formulas cover every setting. The lowest possible total is the number of dice plus the modifier. The highest is the number of dice times the sides, plus the modifier. The average total is the number of dice x (sides + 1) / 2, plus the modifier. So 3d6 runs from 3 to 18 with an average of 10.5, and 1d20+5 runs from 6 to 25 with an average of 15.5.

A single d20 lands on any chosen number 5 percent of the time. If you roll two d20 and want at least one 20, the chance is 1 - 0.95 x 0.95 = 9.75 percent. Doubles on 2d6 happen 6 times in 36, or 16.7 percent. The average in the note is the mean of the dice in that one roll, so it will wobble around the expected value from roll to roll.

Tabletop role-playing games such as Dungeons and Dragons use d4, d6, d8, d10, d12 and d20, with d100 for percentile rolls. Here d100 gives a number from 1 to 100 directly, so you do not need a pair of ten-sided dice. Board games usually need 2d6 or a single d6, and teachers use dice to show probability: roll 2d6 thirty-six times and 7 should appear about six times, though it rarely appears exactly six. Copy the totals into the average calculator to see how they cluster. More dice also pull results toward the middle: one d6 is flat from 1 to 6, while 3d6 bunches around 10 and 11 and rarely reaches 3 or 18, which is why games use different dice for different feels. Choose a die by the spread you want: d4 gives small steps, d20 gives wide swings, and d100 gives fine percentages.

• A 7 is the most common total on two dice, but on one die every face is equally likely.
• The modifier is added once. 2d6+3 is the total of two dice plus 3, not 3 added to each.
• A hot streak is not a pattern. Each roll is independent, like a flip of the coin flip tool.

The tool deliberately stays simple. It does not include advantage or disadvantage, drop-lowest, exploding or rerolled dice, custom faces or saved rolls. Because every die is shown, you can handle some of these by eye: roll 2 dice with d20 and take the higher one for advantage, or roll 4d6 and ignore the lowest. To pick who goes first, try the wheel spinner with player names, or use the random number generator for ranges that dice do not cover.