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Every D&D player knows the iconic twenty-sided die. It’s the heart of the game, deciding the success and failure of our heroes and creating those unforgettable moments at the gaming table. But what if we used two ten-sided dice instead of the 1d20? This seemingly small change would have dramatic effects on the entire feel of Dungeons & Dragons.
The Mathematics Behind the Dice
To understand why this change would be so significant, we first need to look at probability distributions. In the classic 1d20 system, each result from 1 to 20 has exactly the same probability of 5%. This flat or uniform distribution means that a 1 is just as likely as a 20 or an 11.
With 2d10 (where both dice are added together for a result between 2 and 20), a bell curve emerges instead. The middle values around 10-12 are significantly more likely than the extremes. An 11, for example, has a 10% probability, while both 2 and 20 occur with only 1% chance.
The Practical Effects
These mathematical differences have concrete consequences for the game:
- Average results become more frequent: Players would experience “average” successes more often
- Critical successes and failures become rarer: The infamous “Natural 1” and “Natural 20” would become true rarities
- Predictability increases: The game would feel less chaotic and random
How Bonuses and Penalties Would Feel
A particularly interesting aspect concerns the effect of modifiers. The Player’s Handbook 🛒 shows us how important bonuses are for character development. In a 2d10 system, however, these would feel completely different.
A +5 bonus with 1d20 shifts the entire curve evenly upward – every number is increased by 5, the distribution remains flat. With 2d10, however, the bell curve is shifted, causing the bonus to work differently depending on which area of the curve is affected.
Example from Practice
Imagine a fighter who wants to hit a difficult Armor Class of 18:
- With 1d20 + 5: He needs a 13 or higher (40% chance)
- With 2d10 + 5: He also needs a 13 or higher, but the probability is about 21%
The fighter would be significantly less successful, even with identical bonuses!
The Impact on Different Game Aspects
Combat System
In combat, a 2d10 system would lead to fewer spectacular moments. Critical hits (Natural 20) and critical failures (Natural 1) would be extremely rare. At the same time, combat would run more predictably, as extreme outliers up or down would be less common.
Skill Checks
For skills, the 2d10 system would be particularly noticeable at high difficulty classes. A DC 20 roll would be practically impossible without massive bonuses, while medium difficulty classes would be achieved more frequently.
Saving Throws
Saving throws would become less “all or nothing.” The dreaded Natural-1 failures would be history, but the saving Natural-20 successes would also become absolute exceptions.
Why D&D Stayed with 1d20
The decision for the 1d20 system wasn’t random. Gary Gygax and the early D&D developers deliberately wanted a system that:
- Enables dramatic turns: Every roll can surprise
- Rewards heroic deeds: Even weaker characters can accomplish great things with luck
- Is simple to understand: Every roll has the same basic chances
- Creates tension: Until the die stops rolling, anything is possible
Other Systems as Inspiration
Interestingly, many other role-playing systems do rely on bell curves. The classic 3d6 system for ability scores in older D&D editions is an example of this. Modern systems like GURPS also use 3d6 for their basic rolls.
These systems deliberately create a different gaming feel – less chaotic, but more consistent and predictable. Whether that’s better or worse depends on the preferences of the gaming group.
Conclusion: Different Dice, Different Stories
The choice between 1d20 and 2d10 is ultimately a decision about the kind of stories we want to tell. D&D’s flat 1d20 system creates wild, unpredictable adventures where any moment can change everything. A 2d10 system would instead create calmer, more consistent stories where competence and preparation are more important than luck.
Both approaches have their justification, and as Dungeon Masters we can use these insights to consciously shape our game. Maybe you’ll try 2d10 in your next one-shot? The Dungeon Master’s Guide 🛒 provides further guidance for house rules and system modifications.
Ultimately, D&D isn’t about perfect mechanics, but about shared stories and unforgettable moments at the gaming table. Whether these arise through a twenty-sided die or two ten-sided dice is secondary – the main thing is that you have fun with it!
