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Bounded Accuracy D: A Simple Guide to a Core Design Principle of 5e D&D

Bounded Accuracy D: What It Is and How It Affects Your Game


If you are a fan of Dungeons & Dragons, you might have heard of a term called "bounded accuracy". But what does it mean, and how does it impact your gameplay? In this article, we will explain what bounded accuracy is, how it works in 5e D&D, and what are its pros and cons. Whether you are a player or a DM, understanding bounded accuracy can help you enjoy the game more and create better stories.

Bounded Accuracy D

What is bounded accuracy?

Bounded accuracy is a design principle in 5e D&D that limits the numeric bonuses we add to our d20-based rolls. Changes made to the bonuses from previous editions allow us to focus more on how many hits a character can take and what abilities they have, rather than just looking at the numbers.

The term itself is pretty simple. "Bounded" means to be restricted within certain limits, while "accuracy" refers to how hard it is to do something. Put them together and we get: "A set of limits on how hard it can be to do something."

When we look at the roll of a d20, there are 20 different options. Shocker, right? It's the basis of how we decide whether or not we're capable of doing something. If bonuses didn't exist at all, we'd be looking at a system where everyone had the same chance of succeeding on a task whenever they roll the dice. We'd also never be able to roll anything above a 20, that would be impossible.

In 5e, we do have bonuses, but they're not as insane as they have been in previous editions. Now we have some limits as to how high of a roll you can get, or how good you can be at something.

What are the limits in 5e?

The highest roll possible for your average character in 5e is a 30. That number is arrived at by combining our natural dice rolls with any modifiers available. This creates consistency, setting 30 as the maximum DC, AC, and CR throughout 5e.

  • Natural Dice Rolls. On a d20, there are actually only 18 numbers we care about. Since a 1 is a critical failure and a 20 is a critical success, it's everything in the middle that actually gets brought into calculation. This means that the highest roll that counts on a d20 is typically a 19.

  • Proficiency. In 5e, every character has the same progression for proficiency bonuses. These bonuses start at 1st level with +2 and end at 20th level with +6. There are a few classes that get the expertise ability, allowing them to add their bonus twice, but we'll treat this as an outlier.

  • Ability Modifier. Characters in 5e have an ability score cap of 20, meaning they won't pass above a +5 modifier except for in extremely specific circumstances.

How does accuracy work in 5e?

The modifiers we apply to any roll of the d20 let us know how good we are at doing something. Since the typical maximum modifier is 11, our scale of possibilities is anywhere from -3 to 30. This gives us a relatively small range to determine the difficulty of a task. It's for this reason that any check requiring the roll of a d20 can be split into the following table.




Very easy


Tying your shoes



Climbing a low wall



Picking a lock



Swimming in rough water

Very hard


Disarming a trap

Nearly impossible


Jumping across a chasm

This means that even a low-level character can attempt a very hard or nearly impossible task, and have a slim chance of succeeding. Conversely, even a high-level character can fail at an easy or medium task, if they roll poorly. This creates a sense of uncertainty and excitement, as well as realism and fairness.

Benefits of bounded accuracy

Bounded accuracy is not just a random choice by the designers of 5e. It has several advantages that make the game more enjoyable and engaging for both players and DMs. Here are some of them:

Simplicity and consistency

Bounded accuracy makes the game easier to learn and play, as well as more consistent across different levels and scenarios. You don't have to worry about keeping track of dozens of modifiers, bonuses, penalties, and special rules that change depending on your level, class, equipment, or situation. You just roll a d20, add your modifier, and compare it to a DC or AC that is usually within the same range.

This also makes the game faster and smoother, as you don't have to spend time calculating or looking up numbers, or arguing about rules. You can focus more on the story, the action, and the fun.

Balance and diversity

Bounded accuracy makes the game more balanced and diverse, as it allows for more options and combinations of characters, monsters, and encounters. You don't have to worry about being outclassed or irrelevant by other characters or enemies that have much higher or lower numbers than you. You can play any class, race, or build you want, and still contribute to the party and the adventure.

This also makes the game more flexible and adaptable, as you can use any monster or encounter from any source or level, and adjust it easily to fit your campaign. You don't have to worry about finding the right challenge rating or encounter level for your party. You can mix and match different types and levels of enemies, and create interesting and varied scenarios.

Creativity and challenge

Bounded accuracy makes the game more creative and challenging, as it encourages you to use more than just numbers to overcome obstacles and enemies. You don't have to rely on just rolling high or having high bonuses to succeed. You have to think outside the box, use your skills, abilities, items, environment, allies, tactics, and strategies to gain an edge or overcome a disadvantage.

This also makes the game more rewarding and satisfying, as you feel more accomplished and proud when you succeed at something difficult or impossible. You also feel more invested and immersed in the story and the world, as you face real dangers and consequences.

Drawbacks of bounded accuracy

Bounded accuracy is not perfect, however. It also has some drawbacks that might make the game less enjoyable or appealing for some players or DMs. Here are some of them:

Lack of customization

Bounded accuracy makes the game less customizable and personalized, as it limits the options and choices you have to improve your character or monster's numbers. You don't have as many ways to increase your modifiers, bonuses, penalties, or special rules that make you stand out or excel at something. You might feel less attached or interested in your character or monster's progression or development.

This also makes the game less varied and diverse, as you might encounter more situations or enemies that are similar or identical in terms of numbers. You might feel less challenged or surprised by what you face.

Reduced power fantasy


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