Using dice

Objectives for this tutorial

  • Learn how dice help decide results in D&D
  • Learn how to roll dice, including online sites
  • Become familiar with the notation for rolling dice

Refereeing relies on rules

In the first tutorial, you learned that a Dungeon Master performs three activities during a game: setting the scene, reacting to characters, and refereeing the game.

The first two activities rely a lot on your creativity. The way you see the world as the Dungeon Master greatly determines what is in it and how things work. That’s why so much is in your hands as to what is in a scene or how the world reacts to player actions.

The third activity is a little different. Refereeing the game uses more of the game’s rules. The rules are different because they exist in shared resources; e.g. the Player’s Handbook.

For setting the scene or reacting, players rely totally on you to describe the scene that exists in your notes and in your head. For refereeing, players have more more absolute expectations of the rules.

Let’s save the specifics of those rules for later. In this tutorial, we talk about the rules in general. This includes the philosophy underlying Dungeons & Dragons’ rules, meaning the approach that D&D uses most to handle different situations.

Decision making in D&D

The rules in Dungeons & Dragons help you decide how to react in response to a player character’s actions. Applying the rules, which is the bulk of refereeing, often happens as part of you deciding how to react. The rules often use a roll of dice to randomize an outcome when it’s not already known when a character will succeed or fail.

When you roll a die, it’s not already known what result you will get. D&D uses that uncertainty for several different effects. Like all things we discuss, the effects are related, and you may prefer one over the others in your game.

  • Simulation: Simulate likelihoods of possible results. This attempts to model reality in the game world. An example from the real world would be a weather forecast of that predicts a 20% chance of rain. D&D would answer if it rains in a particular location by rolling dice to check if that 20% chance happens.
  • War gaming: Create exciting confrontations between heroes and villains. By introducing an element of the unknown, players and the DM must respond to the new situation. This is very true in combat. An example might be a fight against a thieving highwayman. When a character attacks with a dagger, does the highwayman get stabbed? D&D finds the answer by rolling dice to determine if the character hits the highwayman and how much damage is dealt.
  • Story-telling: Narrate story elements, such as plot twists, unknown to all particpants. An example might be choosing if the person being rescued is madly in love with one of the characters or comes from a family very much opposed to one of the characters, or both! The purpose here is to serve the story that emerges during your game. Note that random doesn’t necessarily have the same story-relevant decision that an author would bring to a plot twist. Games yield a different form of story.

All three effects compete with each other. By this we mean that the more you focus on one aspect, the less the other aspects will be present in your game. There is no absolutely correct mix. Different groups of players prefer different concentrations of simulation, war gaming, and story-telling. Finding the right mix and adjusting the mix is an advanced topic covered in the Resources.

For now, it’s enough to know that D&D uses dice to randomize the outcome of an action.

When to use dice

Note the statement above:

Use a roll of dice to randomize an outcome when it’s not already known when a character will succeed or fail.

What’s interesting is the part about “not already known”. This is because different game worlds have different expectations for what will automatically succeed or fail for a given character.

How is this the case? Imagine an example where a player states that her character is going to fly up to ledge high above and search the nest of twigs built upon the ledge. The ledge is easily a tree’s heigh above, and a strong wind blows. “Fly?” That seems impossible for a person today. Let’s examine different games where a player might ask for her character to fly.

  • How could this be expected to automatically fail? Pretty easily in a lot of game worlds like our own. Failure would be automatic if we say these two things were true: 1) Your game world resembles Tolkien’s Middle-Earth. 2) The character is a human with no magic and no giant eagles nearby. In this case, there is no chance of success. In your response you describe how flight is impossible for the character. Then you ask what else would the player like to try.
  • How could this be expected to automatically succeed? Not the case in most stories, but how might flight be expected? Success would be automatic if we say these two things were true: 1) Your game world resembles our world four thousand years ago. 2) The character is the winged child of a human and an angel. In this case flight is innate for the character. There is no chance of failure, because the character’s divine heritage ensure success. In your response you describe how the character quickly ascends with a few flaps of her wings. You say what she sees in the nest and ask what she wants to do next.
  • How could this both possibly succeed and possibly fail? Look for circumstances that could muddy the outcome. Perhaps the character has an unruly flying beast to use as a mount, such as a flying horse or a large dragonfly. Or, perhaps the character wear an alchemist’s rocket pack that doesn’t have all of the kinks worked out. Or, prehaps the character must first avoid poisonous needles of the Curare trees that make a canopy above. Any of these introduces complications that make the result uncertain.

When it’s not obvious that the character will succeed or that the character will fail, then you roll dice.

Rolling dice

Dungeons & Dragons uses dice to answer two different questions:

  • Does something succeed?
  • To what degree?

D&D uses six different shapes of dice. You are familiar with six-sided dice from other games, such as Yahtzee or Monopoly. The new shapes of dice in D&D are the four-sided die, eight-sided die, ten-sided die, twelve-sided die, and twenty-sided die.

These pictures show all six of the different shapes of dice, though they both have a second type of ten-sided die that has two digits on each of its faces. (It help roll percentages, or 1d100, as explained below.) and

D&D uses a twenty-sided die to answer if something succeeds. The degree of an action can be determined by any dice, sometimes even a mix.

Because rolling dice is so common in D&D, it has a shortened way of writing what dice to roll.

[number of dice]d[size of dice] + [modifier]

The implication is that you roll a number of dice of some size, add their results together, and adjust it by the modifier. It’s a little odd, but you should start reading the expression with the [size of dice].

For example, “1d20 + 1” means the “size of dice” is twenty-sided, the “number of dice” to roll is one twenty-sided die, and afterwards add a “modifier” of one to the result.

Give this a try. If you don’t have an actual set of dice, use an online die roller.


If you are using the first option, you would click on the “d20” button once. Then add one to the number it shows. If you are using the second option, you would type “1d20 + 1” in the edit box labelled “Dice to roll”, then click the “Roll!” button.

Sometimes a game will write numbers that you don’t have dice with that actual size. “d100” is the most common pecial case. This means to roll two ten-sided dice. One of them is the tens digit, the other is the ones digit. Or with an online die roller, you can click the “d100” button.

Some other sizes are a little harder. “d3” can be a six-sided die divided by two. I.e., rolling 1 or 2 on the six-sided equals a result of 1, 3 or 4 on the six-sided die equals a result of 2, and 5 or 6 on the six-sided die equals a result of 3.

Here are some more examples with explanations. Try each of these, either with your own dice or at an online die roller, and compare with the range of the expected result.

  • 3d6 means to roll three six-sided dice and add their numbers together. The result will be between 3 and 18, with most results closer to 11.
  • 3d6 + 4 means to roll three six-sided dice, add their numbers together, and then add four. The result will be between 7 and 22, with most results closer to 15.
  • 2d20 – 1 means to roll two twenty-sided dice, add their numbers together, and then subtract one. The result will be between 1 and 39, with most results closer to 20.
  • 2d10 + 3 means to roll two ten-sided dice, add their numbers together, and then add three. The result will between 5 and 23, with most results closer to 15.
  • 1d100 + 3 means to roll two ten-sided dice. Use one dice as the tens digit and the other as the ones digit, then add three. The result will be between 4 and 103, with results uniformly distributed over the whole range. Note how this is different than the previous example, even though both of them use two ten-sided dice.

Overview of the example game

This example covers a portion of the example in the first tutorial, focusing on when the player’s need to roll dice. It adds notations for the dice that participants roll in bold. Try rolling your own dice and see how you compare.

The participants in this portion of a D&D game are

  • Desiree, the Dungeon Master running the game
  • Erika, a player controlling the character Freya. Freya is a fierce and formidable fighter.
  • Quinn, a player controlling the character Rozh. Rozh is a larcenous, laconic rogue.
  • Vince, a player controlling the character Wyst. Wyst is a wily but weak wizard.

Script from the example game

Desiree (DM): The three of you have walked outside town to the forest clearing that has the abandoned tower. A light breeze rustles the leaves and chills your skin. It’s chill in the shadows, though you quickly warm in the mid-morning sun in the clearing. You see the tower, made of crumbling stone, rising 30 feet. There’s also a tidy cottage in much better repair. You know that a wizard named Thariel used to live in the cottage.

Erika (Freya): “This is the place, friends.” Does Freya see any entrance to the tower?

Desiree (DM): Yes, there’s an iron-bound door with a rusted padlock settled into its latch.

Erika (Freya): Then Freya will bash the door down!

Desiree (DM): Make a Strength check, Difficulty Class 10.

Erika (Freya): <rolls> Yes! I got an 11.

Desiree (DM): Freya throws her shoulder into the door and it slams open with a THUD.

Inside the tower, you smell decay and rot.

There’s movement to your right. What looks like a man’s corpse rises from the floor, groans, and charges at you!

Vince (Wyx): I anticipated danger such as this. I cast a Magic Missile spell at the corpse.

Desiree (DM): First, I need all three of you to roll initiative. Vince, Wyx has been ready, but he also has been hanging back with a restricted view. I’d say Wyx has no special modifiers at this time.

Vince (Wyx): <rolls> But then again, I rolled an 18, so it looks like I was prepared after all!

Desiree (DM): Indeed you were. What did you get for your characters’ initiatives, Erika and Quinn?

Quinn (Rozh): <rolls> Only a 7.

Erika (Freya): <rolls> Freya has an 11 initiative.

Desiree (DM): Then Wyx acts first, as this rotted body rushes towards Freya.

Vince (Wyx): I cast Magic Missile with stentorious intonation and carefully controlled gestures. As three glowing orbs of force race to the creature, I sniff distastefully at the air. “Likely only a zombie, but it tells us something of what’s happening here.”

Desiree (DM): Okay Mr. Magic, how much damage do your orbs of force inflict upon this lifeless body?

Vince (Wyx): <rolls> I do 12 points of force damage.

Desiree (DM): The magic missiles blast into the body, tearing large holes in its chest. Momentum carries it forward, even as it falls to the ground, moving no longer.


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