BASIC D20 TO CHAOSIUM BRP
Basic d20 is a simplified version of the d20 system suitable for use in any d20-based campaign. Thissystem has been designed for quick character generation and ease of play. The focus is to make it
simpler for players. The GM, however, must be well-versed in the d20 system to make use of this set ofrules. The system cannot be used with other gaming systems without conversion, however. This
document explains how to convert your Basic d20 character for use in Chaosium’s Basic RolePlaying
Game modules and adventures.

ABILITY SCORE CONVERSION
Convert your Basic d20 ability score modifiers to Chaosium characteristics according to the table below.
Ability Score in
Basic d20-4-3-2-1+0+1+2+3+4+5Chaosium BRP
Characteristic
3
4-5
6-7
8-9
10-11
12-13
14-15
16-17
18-19
20-21

Ability or Statistic in
Basic d20
Strength
Dexterity
Constitution
Intelligence
WisdomCharismaHeight & Weight (See Table)
13 + Int + Wis

Characteristic in
Chaosium BRP
STR
DEXCONINT
POW
APP
SIZ
EDU

To use the table, simply take your Basic d20 ability score modifiers and read across until you find theappropriate characteristic in the Chaosium BRP. If a range is given, the GM can assign a number or makethe player roll to see exactly what ability score the character has.
For example, the GM decides to run the Masks of Nyarlathotep campaign in Call of Cthulhu. Onecharacter has Str +2, Dex +2, Con +3, Int +0, Wis -1, and Cha +2. The generous Keeper decides to givethe player a 50% chance to have the higher of the two scores listed for each characteristic. After rollingfor each characteristic, these scores become STR 14, CON 17, INT 10, POW 8, DEX 15, and APP 14.
Looking at the character’s listed height and weight, he assigns SIZ 12. He decides to make EDU equal to
13 plus the character’s Basic d20 Intelligence and Wisdom ability score modifiers, for a total of 12. Well,
at least he graduated from high school!
As gleaned above, it is recommended that you use the following formula for EDU:EDU SCORE = 13 + BASIC D20 INT + BASIC D20 WIS

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Use the chart below to determine the character’s SIZ score. To use the chart, find the row containing
the character’s listed height in either inches or centimeters. Note the SIZ score given for that height. Onthe same row, look to the right to find the range of weights associated with that SIZ score. If yourcharacter’s weight falls within the range given, keep the SIZ that you noted. If your character’s weight is
not within the range, move up or down until you find the first range containing your character’s weight.
Use this row to find your character’s SIZ.
SIZScore
12345678
910111213
14
15
16
17
18
192021222324
25

Character Height
Inches
0-12
13-24
25-36
37-42
43-48
49-54
55-60
61-62
63-64
65-66
67-68
69-70
71-72
73-74
75-76
77-78
79-80
81-82
83-84
85-86
87-88
89-90
91-92
93-94
95-96

Character Height
Centimeters
0-30
31-60
61-90
91-104105-120121-135
136-150
151-155
156-160
161-165
166-170
171-175
176-180
181-185
186-190191-195
196-200
201-205
206-210211-215
216-220221-225
226-230
231-235236-240

Character Weight
Pounds
0-20
11-40
21-60
31-80
41-10051-12061-14071-16081-18091-200101-220111-240
121-260131-280
141-300
151-320161-340
171-360
181-380191-400
201-420
211-440
221-460
231-480241-500

Character Weight
Kilograms
0-10
5-20
10-30
16-40
21-50
26-60
31-70
36-80
41-90
46-10051-11056-12061-13066-14071-15076-16081-17086-18091-19096-200101-210106-220111-230
116-240
121-250

Example #1: Your character is a half-elf that’s 5’4” and weighs 145 lbs. This is 64 inches. The playerfinds that 64 inches is in the “9” row for SIZ. Looking right, he notices the weight range for SIZ 9 is “81180.” Since 145 lbs. falls within this weight range, his character has SIZ 9.
Example #2: Your character is an extremely tall valley elf. He is 6’ and weighs 115 lbs. The player findsthat a 72 inch character should have a SIZ of 13, but since 115 lbs. is not within the weight range for thatSIZ, he must record 12 for his character’s SIZ (since 115 lbs. is found in the range for SIZ 12).
Example #3: A large, short dwarf is 47” tall and 144 lbs. His SIZ is 8.

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HIT POINT CONVERSION
Find your character’s hit points based on his Toughness skill ranks only. Toughness feats don’t count.
Round numbers normally.
Toughness
Skill Ranks
01234567891011121314151617181920

ChaosiumBRP(CON+SIZ) X 50%(CON+SIZ) X 55%(CON+SIZ) X 60%(CON+SIZ) X 65%(CON+SIZ) X 70%(CON+SIZ) X 75%(CON+SIZ) X 80%(CON+SIZ) X 85%(CON+SIZ) X 90%(CON+SIZ) X 95%
CON+SIZ (or “Total Hit Points”)
CON+SIZ+1
CON+SIZ+2
CON+SIZ+3
CON+SIZ+4
CON+SIZ+5
CON+SIZ+6
CON+SIZ+7
CON+SIZ+8
CON+SIZ+9CON+SIZ+10Average PC
Hit Points
121314151617182021222324252627282930313233

CONVERTING POWER POINTS SPENT TO SKILL POINTSTo figure out the number of skill points your Basic d20 character has for use in a Chaosium adventure,use the following formula.
SKILL POINTS = (PP SPENT ON BROAD SKILLS ÷ 400) × 5000
These skill points should be put into Chaosium skills at levels that closely approximate the character’s
Basic d20 broad skills.

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BROAD SKILL CONVERSION
The uses for various broad skills are detailed below for the Chaosium BRP. Skills found in all eras of Callof Cthulhu are also listed. Please note that percentiles in the Cthulhu Mythos skill must be earned thehard way.
Chaosium Basic RolePlaying Game, Call of Cthulhu, and Stormbringer
Skill Equivalents
Climb, Fly, Jump, Ride, Swim, Tumble
Awareness, Balance, Insight, Listen, Scent, Search, See, Sense, Spot, Spot Hidden, Taste,Track
Dodge
Dodge, ShieldFight
Brawl, Fist/Punch, Grapple, Head Butt, Kick, Martial Arts, Melee Weapon
Fortitude-Interaction
Bargain, Command, Etiquette, Fast Talk, Gaming, Orate, PersuadeKnowledge
Anthropology, Archaeology, Evaluate Treasure, History, Knowledge, Library Use, Make
Map, Memorize, Music Lore, Natural History, Navigate, Occult, Plant Lore, Poison Lore,Psychology, Research
Languages‘pande, Common Tongue, Language (Other), Language (Own), Literacy, Melnibonean(High), Melnibonean (Low), Orgjenn, Other Language, Own Language
Parry
Parry, Shield
Performance Art, Disguise, Juggle, Perform, Photography, Sing
Profession
Accounting, Credit, Credit Rating, Law, Status, Strategy, Teach, Tie Knot
Reflex-Science
Astronomy, Biology, Chemistry, First Aid, Geology, Medicine, Pharmacy, Physics,
Psychoanalysis, Psychotherapy, ScienceShootEnergy Weapon, Firearm, Handgun, Heavy Weapon, Machine Gun, Missile Weapon,Projection, Rifle, Shotgun, Submachine Gun, ThrowTechnology
Computer Use, Craft, Demolition, Electrical Repair, Electronics, Mechanical Repair,Repair, Technical Skill
ThieveryAmbush, Conceal, Cut Purse, Fine Manipulation, Hide, Locksmith, Move Quietly, PickLock, Set Trap, Sleight of Hand, Sneak, StealthToughness(See Hit Points)
VehiclesArtillery, Drive, Drive Auto, Drive Carriage, Heavy Machine, Operate Heavy Machine,Pilot, Pilot Balloon, Pilot BoatWilderness-Will-Broad Skills
Athletics
Awareness

CONVERTING ADVANTAGES
Although there are really no feats or class special abilities in Chaosium’s BRP, the GM can consider any
advantages a Basic d20 character has and (perhaps) incorporate them in a roleplaying sense into thecampaign. Some advantages may convert to Powers, but this is at the discretion of the GM.

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CONVERTING POWERSThe Chaosium BRP rulebook has a Powers section. In this section, Magic, Mutations, Psychic Abilities,Sorcery, and Super Powers are detailed. There are too many variations or equivalencies to list here.
What will be detailed is a quick conversion that can be used, with significant GM oversight, to convert
Power Points spent on Powers in Basic d20 to skill points spent on Powers in the Chaosium BRP.
If you decide to convert Basic d20 Power Points to be used with the Magic Power, use the following
formulae to figure out how many skill points your character receives to spend on Magic Power skills.
SKILL POINTS FOR MAGIC POWERS
Game Power Level
Start withNormal
PP Spent on Basic d20 Magical Powers
HeroicPP Spent on Basic d20 Magical Powers
EpicPP Spent on Basic d20 Magical Powers
Superhuman
PP Spent on Basic d20 Magical Powers

And then multiply by101520
25For example, if a player has spent 5 PP to gain 1st level wizard spellcasting ability for his character in
Basic d20, then he should receive 50 skill points to be spent on Magic in a Normal Power Level Game in
the BRP. This closely corresponds to a Chaosium character with INT 13 starting a Normal Power Level
Game with his four initial spells at INT X 1 beginning skill.
If you decide to convert Power Points for use with Psychic Abilities, use the following formulae to findthe number of skill points your character receives for Psychic Abilities.
SKILL POINTS FOR PSYCHIC ABILITIESGame Power Level
Start withNormal
PP Spent on Basic d20 Psionic Powers
HeroicPP Spent on Basic d20 Psionic Powers
Epic
PP Spent on Basic d20 Psionic Powers
Superhuman
PP Spent on Basic d20 Psionic Powers

And then multiply by
481220If you decide to convert Power Points for use with the Sorcery Power, use the following formulae.
LEVELS OF SORCERY POWERS
Game Power Level
Start withNormal
PP Spent on Basic d20 Powers
HeroicPP Spent on Basic d20 Powers
Epic
PP Spent on Basic d20 Powers
Superhuman
PP Spent on Basic d20 Powers

And then multiply by
10%25%50%100%

Then add
INT ÷ 2
INT
INT × 2
INT × 4

If you decide to convert Power Points for use with Super Powers, use the following formula for Super
Powers in all Power Level Games:
CHARACTER POINTS (FOR SUPER POWERS) = PP SPENT ON BASIC D20 POWERS

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WHAT CAN I USE THIS FOR?
Well, assuming that you’ve decided to go ahead and use the Basic d20 system to describe your player
characters, you may find that you want to have them adventure in one of Chaosium’s many fineroleplaying games. Perhaps you are running a d20 Modern campaign and you want to shake things up alittle by running a Call of Cthulhu adventure. Or maybe you just purchased a copy of Stormbringer on
eBay and you think it’d be neat to have your characters run into Elric (and experiment with that gamesystem for a bit).
You can also reverse engineer Chaosium products and run them in Basic d20, if you desire. Simply“reverse” the conversion as described in this document. Translate BRP characteristics into Basic d20
ability score modifiers. Add up the Chaosium skill points that a non-player character has and multiply
these by 0.08 (or divide by 12.5) to find the number of Basic d20 skill points that NPC has (roundnormally). For powers, use Basic d20 equivalents. Remember, most Call of Cthulhu spells and creaturesappear in the d20 version rulebook.
Since Basic d20 is really the “Esperanto of gaming systems” and previous documents have alreadyshown you how to use it for all manner of D&D and d20 systems, it is only natural that latersupplements show you how to convert Basic d20 into other gaming systems. This is the first supplement
along those lines. So, have fun fighting Cthulhu!

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