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COMPARISON OF RPG SYSTEMS

The main purpose of this document is to provide tables based on statistical data, to convert characters and adventures from one RPG system to an other. The conversion values where determined by the analysis of success probabilities for different tasks in the given systems.

Statistic Conversion Tables

These tables assign CORSY stats to the stats of the character. Each character can be converted to CORSY standard stats and the CORSY standard stats can be converted in an other system.

Rating Conversion Tables

These tables allow to convert stat ratings of a character from one system into stat ratings of other systems.

Probability Analysis Tables

These tables are provided as "proof" for the correctness of this system. They show the probabilities of success for a character with a given skill rating at a task with a given difficulty rating.

Definitons

First, it is necessary to explain a few basic terms that are frequently used in CORSY. These terms are used to classify the capabilities of characters and items and the difficulty of tasks performed by them and with them.

Average(AV) Attribute

The Average Attribute the average Attribute Rating of a normal human in the system.

Average Attribute Ratings
FUDGE Alt d20 WEG SW GURPS TNE MMT MT
Fair 10 10 2d 10 6 7 7

Average(AV) Skill

The Average Skill is a skill in the center of the probability range of a rules system. This is usually the lowest common Skill Rating for player characters, with lower Skill Ratings being a definite handicap

Average Skill Ratings
FUDGE Alt d20 WEG SW GURPS TNE MMT MT
Fair 10 +0 3d 10 0 0 0

Abbreviations:
Alt:
Alternity, d20:Wizards of The Coast d20 system, WEG SW:West End Games Star Wars Role Playing Game, TNE:Traveller the New Era, MMT:Marc Millers Traveller, MT:Mega Traveller

Average(AV) Difficulty

The Difficulty Rating, at which a character with AV Skill succeeds 50% of the time.

Attribute Ratings

Attribute Ratings are rated in the following steps (choose your favorite description):

The current conversion of attributes is based on the skill conversion.

Skill Ratings

Skill Ratings are rated as attributes. Two step increases should increase the probability of success by a factor of 2, therefore one step increases probability by a factor of square root of 2.

Difficulty Ratings

Difficulty Ratings are rated in the same manner as skills, but each two step increase decreases probability of success by a factor of 2.

Rating Conversion Tables

The Rating Conversion Tables allow the conversion of a Rating of any RPG System covered in CORSY to any other. Simply find out the row the Rating (or a better Rating) is listed in the column of the Source System and look up the Rating in the column of the Target System.

Attribute Ratings

To convert the Attribute of a Character of one system to an other, select the column headed with the name of the Source System. Then look up the Attribute Rating of the Character in that column. Now stay on the same row you found the Attribute Rating and look up the entry in the column of the Target System. This entry is the Attribute Rating of the Character in the new system.

This table was calculated based on the skill calculation, and how attributes affect it.

Attribute Ratings
Rating FUDGE Alt d20 WEG SW GURPS TNE MMT MT
VL - 4 8 1d 7 3 4 4
LO Poor 6 9 1d+1 8 4 5 5
LA Poor 7 10 1d+2 9 5 6 6
AV Mediocre 10 11 2d 10 6 7 7
HA Mediocre 13 12 2d+1 11 8 8 8
HI Fair 16 13 2d+2 12 10 8 9
VH Fair 18 14 3d 13 14 9 10
XH Good 21 15 3d+1 14 - 10 11
XX+1 Good 26 17 4d 15 - 11 12
XX+2 Great 32 18 4d+1 16 - 12 13
XX+4 Great 42 21 5d+1 18 - 14 15
XX+6 Superb 52 - 6d+1 20 - - -
XX+10 - 73 - 7d+1 24 - - -

*based on difficulty of equal step Rating, not on AV/XH difficulty

Abbreviations:
Alt:
Alternity, d20:Wizards of The Coast d20 system, WEG SW:West End Games Star Wars Role Playing Game, TNE:Traveller the New Era, MMT:Marc Millers Traveller, MT:Mega Traveller

Columns:
Rating: Step Rating of Skill in the CORSY System.
FUDGE: Thread Level of the Attribute in the FUDGE System.
Alt: Ability Score in TSR's Alternity System.
d20: Attribute Level for WotC's d20, 3d edition.
WEG SW: Attribute Level in WEG's Star Wars System.
GURPS: Attribute Level in Steve Jackson Games GURPS.
TNE: Attribute Level in GDW's TNE.
MMT: Attribute Level in Imperium Games MMT.
MT: Attribute Level in GDW's MT.

Conversion Notes:
General: The average Attribute score for a player character is usually above the AV value.
Wizards of The Coast d20 system: Technically, the average modifier to go up one CORSY Rating is about 1.5 to 2. This conversion uses the official Star Wars conversion and is far off. However, if the skills are converted correctly using this system, and the attribute modifier are subtracted, the result will work.

Skill Ratings

To convert the Skill of a Character of one system to an other, select the column headed with the name of the Source System. Then look up the Skill Rating of the Character in that column. Now stay on the same row you found the Skill Rating and look up the entry in the column of the Target System. This entry is the Skill of the Character in the new system.

This table was calculated based on the probability to succeed at a task of Average difficulty and probability to succeed at task of Extremely High difficulty.

Skill Ratings
Rating AV/XH% FUDGE Alt d20 WEG SW GURPS TNE MMT MT
VL 18 - 4 -6 2d 7 -/2 -/4 -
LO 25/6 Poor 5 -5 2d+1 8 -/3 -/5 -
LA 35/9 Poor 7 -3 2d+2 9 -/4 -/6 -
AV 50/13 Mediocre 10 +0 3d 10 0/5 0/7 0
HA 70/18 Mediocre 13 +3 3d+1 11 1/7 1/8 1
HI 100/25 Fair 16 +5 3d+2 12 3/10 1/8 2
VH /35 Fair 18 +6 4d 13 7/14 2/9 3
XH /50 Good 21 +8 4d+1 14 14/20 3/10 4
XX+1 /70 Good 26 +10 5d 15 22/28 4/11 5
XX+2 50* Great 32 +11 5d+1 16 36/40 5/12 6
XX+4 50* Great 42 +14 6d+1 18 - 7/14 8
XX+6 50* Superb 52 +17 7d+1 20 - - -
XX+10 50* Superb 73 +23 9d+1 24 - - -

*based on difficulty of equal step Rating, not on AV/XH difficulty

Abbreviations:
Alt:
Alternity, d20:Wizards of The Coast d20 system, WEG SW:West End Games Star Wars Role Playing Game, TNE:Traveller the New Era, MMT:Marc Millers Traveller, MT:Mega Traveller

Columns:
Rating: Step Rating of Skill in the CORSY System.
AV/XH%: Indicates optimum probability (in %) a character of that Skill Rating would have to succeed in a task of AV respectively XH difficulty.
FUDGE: Thread Level of the Skill in the FUDGE System.
Alt: Skill Score in TSR's Alternity System.
d20: Total of modifiers on the die roll for WotC's d20 system.
WEG SW: Skill Level in WEG's Star Wars System.
GURPS: Skill Level in Steve Jackson Games GURPS.
TNE: Skill Level and Asset (separated by a slash) in GDW's TNE.
MMT: Skill Level and Skill Level plus Attribute (separated by a slash) in Imperium Games MMT.
MT: Skill Level in GDW's MT.

Conversion Notes:
Wizards of The Coast d20 system: To convert a character the total of attribute bonus + skill should be equal to the modifier listed in the column. To get the raw skill bonus, subtract the attribute bobus from the result in the column.
Traveller New Era: It may be better to use the Asset instead of the Skill to convert to/from GDW's TNE.
Marc Millers Traveller: It may be better to use the Attribute associated with the skill plus skill level for the conversion.

Difficulty Ratings

To convert the Difficulty of a task of one system to an other, select the column headed with the name of the Source System. Then look up the difficulty of the task in that column. Now stay on the same row and look up the entry in the same row in the column of the Target System. This entry is the Difficulty of the task in the new system.

Difficulty Ratings
Rating AV% FUDGE Alt d20 WEG SW** GURPS TNE MMT MT
LO 100 Poor -5/-d20 2 Esy/ 7 +2 Esy Esy Esy
LA 70 Mediocre -3/-d8 7 Esy/ 9 +1 - - -
AV 50 Mediocre +0/+d0 11 Mod/11 +0 Avg Avg Rtn
HA 35 Fair +1/+d4 14 Mod/13 -1 - - -
HI 25 Fair +3/+d8 16 Mod/14 -2 Dif Dif 9+
VH 18 Good +4/+d12 17 Dif/15 -3 - - -
XH 13 Good +5/+d20 19 Dif/16 -4 Frm Frm Dif
XX+1 9 Great +5/+d20 20 Dif/17 -5 - - -
XX+2 6 Great +6/+2d20 21 Dif/19 -6 Imp Stg 13+
XX+4 25* Superb +7/+3d20 25 VDf/23 -8 - Imp Frm
XX+6 25* Superb +8/+4d20 28 VDf/26 -10 - - -
XX+10 12* - +9/+6d20 34 VDf/33 -14 - - -

*probability based on XX+2/XX+4/XX+6 skill, not on AV skill.

Abbreviations:
Alt:
Alternity, d20:Wizards of The Coast d20 system, WEG SW:West End Games Star Wars Role Playing Game, TNE:Traveller the New Era, MMT:Marc Millers Traveller, MT:Mega Traveller
Esy:Easy, Mod:Moderate, Avg:Average, Rtn:Routine, Dif:Difficult, VDf:Very Difficult, Frm:Formidable, Stg:Staggering,Imp:Impossible

Columns:
Rating: Step Rating of Difficulty in the CORSY System.
AV%: Indicates optimum probability (in %) a character with AV Skill level would have to succeed in a task of the given Difficulty. The number in the % column lists the actual probability if character/adventure is converted using this system.
FUDGE: Difficulty of the Task in the FUDGE System.
Alt: Difficulty Step and Situation Die (separated by a slash) of the task in TSR's Alternity System.
d20: Difficulty Class of the die roll in WotC's d20 system.
WEG SW: Difficulty and Difficulty Number (separated by a slash) of the task in WEG's Star Wars System.
GURPS: Modifier to base skill in Steve Jackson Games GURPS.
TNE: Difficulty in GDW's TNE.
MMT: Difficulty in Imperium Games MMT.
MT: Difficulty in GDW's MT, or a theoretical minimum die roll introduced to allow a better conversion.

Character conversion process

To finaly convert a character is a lot more complicated than just looking up ratings. The man problem is the extreme difference in basic attributes the different systems use. The recommended method is:

  1. Convert the skills
  2. Determine the attributes/level
  3. Determine advantages/disadvantages/feats
  4. Determine derived values

Convert the skills

Try to figure out the corrosponding skills in the different systems. Take each skill rating of the character in the source system, convert it to the target system and assign it to a similar skill in the target system.

If there are several skills in the source system matching one skill in the target system, the following methods are recommended:

The method used is of course determined by the gamemaster, not the player.

If one skill in the source system matches several skills in the target system, the usual method is to assign the skill rating to all matching skills in the target system.

Determine the attributes/level

Most attributes are best determined not by trying to convert them from the source system, but by looking at the skills. The only exception is the attribute governing hand weapon damage(Strength in most cases). This could be converted using the Attribute ratings table, but I will try to create a special table for this purpose in the future.

The d20 System level and class is difficult to find. A guideline for the class may be the most important skill of the character. Choose the class that would get the best bonus for that skill. If there are several very high skills the character may have to be multiclassed. Then figure out the worst skill rating in a skill important for that class. The bonus in that skill is a good indicator for the characters level.

For all other attributes, figure out the lowest important skill in the target system, that is governed or modified by that attribute in the target system. Then give the character the highest possible attribute rating that would allow a skill rating that low. If you can easily figure out an attribute in the source system that is clearly similar to the attribute in the target system, you may use the Attribute Rating table and find out which result fits better to the character concept and choose any of the two values or a value in between.

Determine advantages/disadvantages/feats

Try to figure out which advantages/disadvantages/feats fit into the character concept or may be converted from the source system. Some odd results in the skill values may be explained by an advantage, disadvantage or feat.

Determine derived values

Determine derived values as described in the rules of the target system.

Probability Analysis Tables

Probability To Succeed At Average(AV)/Extremely Difficult(XH) Task

Success Probability At AV/XH Task
Rating AV/XH% FUDGE Alt d20 WEG SW** GURPS TNE MMT MT
VL 18 18/- 20/6 20/5 17/4 16 20/5 17/2 -
LO 25/6 38/6 25/7 25/5 24/5 26/2 30/5 28/5 -
LA 35/9 38/6 35/9 35/5 33/7 38/5 40/10 42/9 -
AV 50/13 62/18 50/14 50/10 52/12 50/9 50/10 58/16 58/8
HA 70/18 62/18 65/22 65/25 63/17 63/16 70/15 72/26 72/16
HI 100/25 82/38 80/31 75/35 75/23 74/26 95/25 72/26 83/28
VH /35 82/38 90/39 80/40 84/38 84/38 95/35 83/38 92/42
XH /50 94/62 95/52 90/50 90/48 91/50 95/50 92/50 97/58
XX+1 /70 94/62 /72 95/60 97/71 95/63 95/70 97/63 /72
XX+2 50* 62 54 55 52 50 50 50 58
XX+4 50* 38 52 50 49 50 - 56 58
XX+6 50* 62 50 50 53 50 - - -
XX+10 50* - 50 50 53 50 - - -

*based on difficulty of equal step Rating, not on AV/XH difficulty
**Star Wars probabilities include "6" results on the wild die, but count "1" as normal rolls.

Columns:
Rating: Step Rating of Skill in the CORSY System.
AV/XH%: Indicates optimum probability (in %) a character of that Skill Rating would have to succeed in a task of AV respectively XH difficulty.
Other: The other columns list the actual probabilities (in %) in the given system if the character/adventure is used in that system.

Probability To Succeed At A Task With Average(AV) Skill

Success Probability With AV Skill
Rating AV% FUDGE Alt d20 WEG SW** GURPS TNE MMT MT
LO 100 82 86 90 91 74 95 83 97
LA 70 62 72 70 75 63 - - -
AV 50 62 50 50 52 50 50 58 58
HA 35 38 38 35 31 38 - - -
HI 25 38 28 25 23 26 25 29 28
VH 18 18 20 20 17 16 - - -
XH 13 18 14 10 12 9 10 16 8
XX+1 9 6 14 5 9 5 - - -
XX+2 6 6 2 5 5 2 5 5 58
XX+4 25* 38 21 35 21 26 - 34 58
XX+6 25* 38 22 35 26 26 - - -
XX+10 12* - 9 20 11 9 - - -

*probability based on XX+2/XX+4/XX+6 skill, not on AV skill.

Columns:
Rating: Step Rating of Difficulty in the CORSY System.
AV%: Indicates optimum probability (in %) a character with AV Skill Rating would have to succeed in a task of the given Difficulty.
Other: The numbers in the other columns list the actual probability if character/adventure is used in that system.