Dice Roller

How to use it

1. Set the dice and sidesEnter how many dice to roll, from 1 to 20, and choose the number of sides from the menu. The default is two six-sided dice.
2. Press Roll or SpaceEach die is rolled separately. The result line lists every die and, when you rolled more than one, adds them up as the total.
3. Use the tallyUnder the dice, the tally counts how often each face has appeared, kept separately for each die type. Reset clears the tally of the die type you have selected.

What the dice roller does

• Lets you roll a dice of any common shape: d4, a 6 sided dice, d8, d10, d12, a 20 sided dice or d100, chosen in the Sides menu.
• Works as a d20 roller for single checks: set Dice to 1 and Sides to 20 to roll 1d20, then press Space to roll a d20 again.
• Has a d6 roller, d8 roller, d10 roller and d100 roller in the same menu, so you can roll 1d8 for damage as easily as a d20.
• Can roll 2 dice or up to twenty of one kind. Each dice roll is listed and added up, a simple dice calculator for totals; it does not read formulas such as 2d6+3.
• Gives you offline dice for trips: after your first visit, this digital dice roller keeps working without a connection.
• Doubles as a dice simulator for lessons: roll hundreds of times and the tally shows rolling dice settle toward even counts.
• Acts as a virtual dice roller and a plain die roller in one: each face comes from the browser's cryptographic random numbers, so every face has the same chance.

Reading dice notation: 2d6, d20, 3d8

Game books and forums write dice as a count, the letter d, and the number of sides. So 2d6 means two six-sided dice added together, d20 is a single twenty-sided die, and 3d8 is three eight-sided dice. This page maps straight onto that: the Dice box is the number before the d, and the Sides menu is the number after it.

The roller offers d4, d6, d8, d10, d12, d20 and d100, with up to 20 dice at once. It does not type or parse a formula, and it does not add modifiers. For a roll written as 2d6+3, roll 2d6 and add the 3 in your head. When a game asks for different dice together, such as a d8 and a d6, roll each type in turn and add them.

The odds for 2d6, computed

With two six-sided dice there are 36 equally likely combinations. A total of 7 can be made six ways (1+6, 2+5, 3+4 and their reverses), so it comes up 6 times in 36, about 16.7%. A 2 or a 12 needs both dice to show the same extreme face, one way each, so they come up 1 time in 36.

This is why 7 is the favorite and why 6 and 8 are the next busiest totals. If you roll two dice to move around a board, the middle squares are visited most. The table is easy to check by listing the pairs yourself.

From a flat spread to a bell

One die is flat: each face has a one-in-six chance. Add a second die and the totals form a triangle with a peak at 7. Add a third and the shape rounds into a bell: with 3d6 there are 216 combinations, the totals 10 and 11 each have 27 (12.5%), and 3 or 18 each have just 1 (about 0.5%).

That is the reason some games use several small dice instead of one large die. Rolling d20 gives every number from 1 to 20 an equal 5% chance, so extremes are common. Rolling 3d6 makes average results the norm and rare ones really rare. When you design a house rule or pick between two games, decide whether you want swingy outcomes or steady ones, and choose the dice accordingly.

Which die for which job

The d4 and d8 are common in tabletop games, d10 and d100 handle percentages and ranges, the d12 sits between the d10 and the d20 for medium ranges, and the d20 is the usual choice for single checks where every outcome should be possible. Rolling a d100 gives a whole number from 1 to 100, which works as a percentage chance with each value equally likely.

To pick one of N people or items at random, choose a die with at least N sides and roll again if the number is too high; that keeps every choice equally likely. For larger lists or names, the number wheel, name picker and raffle picker do the same job without re-rolling.

How the tally works, and how to test the dice

The tally counts faces, not totals. Rolling 2d6 and getting 3 and 4 adds one to the 3 and one to the 4. Each die type keeps its own tally on this device: switching Sides shows the tally for that die, and Reset clears only the die type you have selected. The tally is still there when you reopen the page.

To check a die, roll 600 single d6s and expect about 100 of each face. Typical spread is around 9 either way: most counts fall between about 90 and 110, and nearly all between 82 and 118. This is also a nice class exercise: each student rolls 60, the class adds the counts, and the flat bars appear as the numbers pile up. Because the page remembers the tally between visits, you can also leave it running over a week of casual rolls and see whether the faces stay close to level.

Repeated rolls: chances worth knowing

The chance of at least one hit in several tries is one minus the chance of missing every time. Rolling a single d6 four times, the chance of at least one six is 1 - (5/6)^4, about 51.8%, a shade better than even. Three rolls give 42.1%. On a d20, three rolls produce at least one natural 20 about 14.3% of the time, and rolling twice and keeping the higher result gives a 20 in 9.8% of cases.

A famous puzzle asks whether 24 rolls of two dice should produce a double six. The answer is slightly under half: 49.1%, whereas 25 rolls tip it over to 50.5%. Nothing is wrong with the dice when a run of 24 fails. Fewer than one in two such runs contains the result, so the miss is ordinary, and you can reproduce it yourself with the tally.

Games, lessons and everyday uses

Board games that tell you to roll the dice and move need no physical dice at the table: a phone or projector does the job, and each player sees the same result at once. Tabletop role-playing groups use the d20 for checks and the other shapes for damage or tables, and remote groups can share a screen. Parents use a die for who goes first, or a d6 to decide chores and bedtime stories. Writers and teachers roll a d6 against a list of six story prompts, and a d20 against twenty vocabulary words, so the choice of the next exercise never rests with the person leading.

In math lessons, 2d6 is a gentle first step into probability. Ask the class to predict the most common total, roll 36 times together, and compare their tally with the table above. For a game of roll-and-add bingo, call totals from 2d6 and let students choose which numbers to cross out, learning along the way that 7 appears most often. A harder challenge for older students is to predict the 3d6 table from the 2d6 one, then roll to find out how close they got. When there are only two outcomes, a coin flip is simpler.