This is a work in progress!
This article attempts to create conversion guidelines for creatures written for the D&D 3E/3.5, d20, and Pathfinder rules. Online stat blocks for such creatures can be found here:
Note, however, that conversion work cannot be an exact science - if you don't think something quite fits for a particular monster, change it!
Quick Reference Table
| D&D Attribute | GURPS Basic Attribute | Secondary Attribute | Advantage/Disadvantage |
| Strength | ST | Basic Lift; Damage | Lifting ST; Striking ST |
| Dexterity | DX | Basic Speed: (HT+DX)/4; Basic Move | Combat Reflexes; Flexibility; Certain Talents |
| Constitution | HT | Basic Speed: (HT+DX)/4 (Extra) Hit Points; (bonus) Fatigue Points | Fit, Very Fit/Unfit |
| Intelligence | IQ | Per | Acute Senses; Eidetic Memory; Certain Talents |
| Wisdom | None | Will; Per (adj) | Acute Senses (adj), Common Sense, Intuition |
| Charisma | None | Charisma, Appearance, Certain Talents, can be "faked" with certain skills. |
Note: Of the examples given in the DMG1 (Julius Caesar, Napoleon Bonaparte, and Adolf Hitler) only the first two actually has Charisma as GURPS defines it. Adolf Hitler by contrast used the skills Performance, Psychology, and Public Speaking to ''simulate'' Charisma.
Attributes
Primary Attributes
ST
Use the following formula for Medium-sized and smaller creatures:
GURPS ST = d20 Strength
Larger creatures will end up comparably weak with this formula. Increase their GURPS ST based on their d20 size category:
| d20 Size Category | ST Modifier |
| Large | +25% |
| Huge | +50% |
| Gargantuan | +75% |
| Colossal | +100% |
DX
Use the following formula:
GURPS DX = 10 + d20 Dexterity Modifier
IQ
Use the following formula:
GURPS IQ = 10 + d20 Intelligence Modifier
HT
Use the following formula:
GURPS DX = 10 + d20 Constitution Modifier
Big monsters in D&D have high Constitution scores since Constitution determines hit points. Regardless of how high the HT score is rolls of 17 and 18 are failures with 18 a critical failure.
Secondary Attributes
HP
Hit Points should generally be set equal to ST.
Will
Per
FP
FP should generally be set equal to HT.
Speed
Derive from DX and HT as normal for GURPS
Move
SM
DR
Use the following formula for the creature's "innate" armor:
GURPS DR = (d20 "natural armor" bonus) / 2
Worn armor should use standard GURPS armor types.
Dodge / Parry / Block
These should be derived as normal for GURPS
Attacks
Afflictions
For attacks that require a reflex save, a Dodge roll should be required to avoid the attack. Treat attacks that require a Fortitude or a Reflex save as Afflictions resisted by HT or Will. The resistance roll should be modified depending on the DC of the attack:
| d20 save DC | GURPS Attribute Modifier |
| 11 or less | +1 |
| 12-13 | 0 |
| 14-15 | -1 |
| 16-17 | -2 |
| 18-19 | -3 |
| 20-21 | -4 |
| 22-23 | -5 |
| … | … |