User Guide

Need help?

If you need any help or have questions or comments about d20, contact me, Blake, the developer at To find out more about d20 and its features, keep reading!

Getting started

The easiest way to get started is to click on the dice you would like to roll and then click the Roll button. You can add multiple dice to your hand (and even modifiers) and then roll them all at once.

Each time you click on one of the dice buttons, they get added to the input field in the form of what I call a dice formula. You can also directly type a formula into the input field if you prefer (d20 tries to construct this formula for you when you click on the various dice and modifier buttons but you may need to type it yourself if you are doing something really complex).

Results show up in a pane on the left. A result consists of a total and a breakdown of each die rolled. It looks something like this:

15   1d20 ( 12 ) + 1d4 ( 3 )

Your last rolled formula stays in the input field so that you can easily roll it again. Or you can clear the input to start a new roll.

If you would rather a die button immediately roll when you click it, you can enable that behavior in Settings.

Now you know the basics of rolling dice in d20. d20’s more powerful features are covered in the rest of this guide. Check out Presets for saving and reusing a formula and Notation for performing more complex rolls.


d20 follows commonly used notation. Here’s an example:

1d20 + 3

That means roll one 20-sided die and add 3 to the result. 2d20 + 3 would do the same thing except it would roll two 20-sided dice instead of one. The dice buttons cover the common dice sizes but you can roll an “imaginary” die of any number of sides up to 1000. For example, 1d42 is a valid formula. If you wanted to simulate flipping a coin, you could roll 1d2.


You can perform math in your formula. We did that in the example above with +3, but you can do more complex math.

Here’s a realistic example. Let’s say you’re playing D&D and you’re rolling a weapon’s damage roll. It’s four d8s. You also get your strength bonus of +5. Your party’s cleric bestowed a spell on you that provides you an extra d4 in damage. Unfortunately the monster has resistance to your damage type, so they’ll only be taking half of the total damage you roll. We could express this like:

(4d8 + 5 + 1d4) / 2

You can perform addition, subtraction, multiplication, and division in your formula. You can even use exponents (maybe you have an overpowered spell that cubes your damage: 2d8^3).

Multiple simultaneous rolls

By default, the entire formula is interpreted to be one roll, which will be totaled. If you would like to make multiple rolls at once, you can separate multiple formulas with a comma. A common use for this in D&D, for example, is to roll for an attack and for damage at the same time. For example, you could do this:

1d20 + 4, 2d8 + 2

By separating two formulas with a comma, we will see two different results displayed in the results pane — one totaling the d20 roll plus the bonus, and the other one totaling the two d8s plus the bonus. Using commas to make multiple rolls at once is made even more powerful when combined with the Presets feature.


Presets are a way for you to define formulas, name them, and roll them with a single click. You will find the Presets pane to the right of the Results pane.

Presets can be placed into groups. You start with just one group, called Default Group. You are encouraged to rename this group as you see fit (e.g., naming it after your character).

Adding a preset

To get started with presets, use the dice buttons or type into the input field to make a formula. Then click Add Preset. A small form will appear where you can give your preset a name and edit the formula. Once you’re happy with it, click Save. The form is replaced with a button. Clicking the button will automatically roll the formula you specified. The result will be labeled with the name of the preset.

Rolling a preset

Roll any preset by clicking its button in the preset list. You will see the result appear in the results pane and it will be labeled with the name of the preset.

Alternatively, the first ten presets have assigned keyboard shortcuts, ⌘1, ⌘2, ..., ⌘0.

I recommend combining presets with multiple-roll notation for rolling attacks and damage at the same time.

Deleting a preset

When you hover your mouse over a preset button, a delete icon will appear on the right side of the button. Click that icon to remove the preset from the list.

Reordering presets

Once you have several presets, you can drag and drop to reorder them. When you hover your mouse over a preset button, a handle will appear on the left. Click and drag the handle to change the position of that preset in the list.

Resizing and closing the presets pane

If you are not using presets, or you just want to temporarily hide them, you can click and drag the vertical line between the two panes to close the Presets pane. Or use the keyboard shortcut ⌘P.

Preset groups

Preset groups are a way to have different lists of presets. For example, you could have a preset group for each of your characters. A drop down menu at the top of the presets pane displays the currently selected group. When you first open the app, the default group is selected.

Click Manage Groups to see a list of all your groups. On the Manage Groups view, you can add a new group, rename any existing groups, and drag and drop to reorder the list similar to reordering presets.

When you create groups here, you will find them in the drop down list on the presets view. Choose any group from that drop down list to see its presets.


You can modify the appearance of the app and a few of its behaviors by visiting the Settings screen. Click Settings in the bottom left of the window, or click d20 in the menu bar navigate to Preferences.


Here you can choose the light or dark theme. By default it is set to auto, which will follow your system setting. You can also make the d20 window float on top of all other windows, as well as remove the background images from the dice buttons if you find them distracting.


Choose whether newly created presets appear at the top or bottom of the preset list.

Turn on Auto-roll if you would like dice buttons to immediately roll a die rather than add dice to your formula.


There are various “Are you sure” style confirmations in the app for clearing or deleting things. You can turn these off if you find them annoying.

Import and export

You can save your settings and presets to an export file so that they can be imported into d20 on another computer. You can access this import / export functionality from the Settings page or by going to the File menu.

Keyboard shortcuts

Function Shortcut
Focus input ⌘ /
Roll ⌘ ⏎
Clear results ⌥⌫
d4 ⌥ Q
d6 ⌥ W
d8 ⌥ A
d10 ⌥ S
d12 ⌥ Z
d20 ⌥ X
Add 1 ⌥ 1
Add 2 ⌥ 2
... ...
Add 9 ⌥ 9
Subtract 1 ⌥⇧ 1
Subtract 2 ⌥⇧ 2
... ...
Subtract 9 ⌥⇧ 9
Roll preset 1 ⌘ 1
Roll preset 2 ⌘ 2
... ...
Roll preset 10 ⌘ 0
Select preset group 1 ⌥⌘ 1
Select preset group 2 ⌥⌘ 2
... ...
Select preset group 10 ⌥⌘ 0
Show/hide presets ⌘ P