2d6 vs TN greater then 12

[jaz0nj4ckal]

Folks,
I am drafting a cheap and quick game that uses 2d6 dice rolls and base success is 7+. I understand that gives me a range of TN 2-12; however, I am looking for target numbers that are greater than 12.

I guess what I am looking for is d20 and TN, but using 2d6. How would I calculate percentages of success for rolls requiring 13+, 14+, etc.

Thank you

 

[Morrus]

Sounds like you're designing Traveller!

I'm not sure I understand the question though. The percentage chance of rolling 13+ on 2d6 is 0%.

 

[jaz0nj4ckal]

Sounds like you're designing Traveller!

I'm not sure I understand the question though. The percentage chance of rolling 13+ on 2d6 is 0%.

I guess you are right I am using sort of the Traveller system; however, I was thinking of using something similar to the d20 TN mechanics. I guess - what is confusing me - is if I set a TN of 13, then the player needs to roll a 12 or (11 + skill of 1 = 12) since 12 is treated as a critical success.

I am trying to extend the Classic Travller rules to have more dice modifiers.

 

[GMMichael]

Here you go. Feel free to mess around with the numbers.

http://anydice.com/

 

[jaz0nj4ckal]

Here you go. Feel free to mess around with the numbers.

http://anydice.com/

Thank you for the link; however, I am not sure how to use this application. I will toy around with it and see if I can make it make sense.

thank you

 

[MatthewJHanson]

I assume PCs can have bonuses to their rolls.

The odds of success will depend on the bonus. Subtract the bonus from the TN, and then figure out the odds for that.

I.E. If they have a +2, to hit a 13 they need to get and 11 on the dice, which would be 3/36.

 

[jaz0nj4ckal]

I assume PCs can have bonuses to their rolls.

The odds of success will depend on the bonus. Subtract the bonus from the TN, and then figure out the odds for that.

I.E. If they have a +2, to hit a 13 they need to get and 11 on the dice, which would be 3/36.

Hmmm I see what you are saying. Do you know what a good baseline or ballpark figure for TN numbers? Do you think they should scale with character skill levels?

I am imagining a system that is very similar to Classic Traveller; however, with higher TN due to different Armor classes and +/- weapons. Sort of in a way - I want to transition D&D/OD&D to use 2d6 dice rolls to keep things simple and use only d6 dice.

Trying to get a OD&D/D&D feel with (2d6+skill+bonus/pen => TN); however, I am not sure where to start with TN values.

NOTE - TN values will be anything built from Armor class and range modifiers.

 

[Nagol]

The answer completely depends on answering the question "Why?"

Mechanics only exist to serve a purpose.

Why are you contemplating a change to the dice rolled? Why does the d20 feel inappropriate? Why use 2d6 instead of 1d6 or 3d6?

 

[jaz0nj4ckal]

The answer completely depends on answering the question "Why?"

Mechanics only exist to serve a purpose.

Why are you contemplating a change to the dice rolled? Why does the d20 feel inappropriate? Why use 2d6 instead of 1d6 or 3d6?

To tell you the truth - I have no major reason - I just wanted to toy around with something with a bell curve. I could use 3d6; however, could I just drop that right into my d20 rolls?

 

[Nagol]

3d6 is a closer fit to d20 in terms of span (16 range compared to 20 with the same centre). There's been some discussion over the years as to how well a 3d6 bell curve replaces a single d20 which you can find easily with google.

In a nutshell, it'll work, sort of. Secondary effects, like critical hit chances, and tertiary effects like the relative value +1 to AC become very different with a bell curve.

I would recommend a different approach though. Rather than picking a mechanic that is different then figuring out its effects, figure out what you want to accomplish then find a mechanic that maps to it.