Advanced Dungeons & Dragons 1st Edition "To Hit" Calculator

To Hit - That number which must be matched or beaten by a 20-sided die roll in order to inflict damage on an opponent. (Advanced Dungeons & Dragons 1st Edition Dungeon Masters Guide p229)

Details of Attacker
Strength of attacker	Monster (no strength "to hit" modifier) (0) 3 (-3) 4-5 (-2) 6-7 (-1) 8-16 (0) 17-18/01-50 (1) 18/51-99 (2) 18/00 (3)
Dexterity of attacker	Monster (no dexterity "to hit" modifier) (0) 3 (-3) 4 (-2) 5 (-1) 6-15 (0) 16 (1) 17 (2) 18 (3)
Magical weapon modifier
Weapon used by Attacker	Axe, Battle Axe, Hand Bardiche Bec de Corbin Bill-Guisarme Bo Stick Club Dagger Fauchard Fauchard-Fork Fist or Open Hand Flail, Footman's Flail, Horseman's Fork, Military Glaive Glaive-Guisarme Guisarme Guisarme-Voulge Halberd Hammer, Lucern Hammer Jo Stick Lance (heavy horse) Lance (light horse) Lance (medium horse) Mace, Footman's Mace, Horseman's Morning Star Partisan Pick, Military, Footman's Pick, Military, Horseman's Pike, awl Ranseur* Scimitar Spear Spetum* Staff, quarter Sword, bastard** Sword, broad Sword, long Sword, short Sword, two-handed Trident Voulge Bow, composite, long Bow, composite, short Bow, long Bow, short Crossbow, heavy Crossbow, light Sling (bullet) Sling (stone) Axe, hand (thrown) Club (thrown) Dagger (thrown) Dart Hammer (thrown) Javelin Spear (thrown)
Class of Attacker	Cleric Druid Fighter Paladin Ranger Magic-User Illusionist Thief Assassin Monk Monster
Level/Hit Dice of Attacker	0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 up to 1-1 1-1 1 1+ 2-3+ 4-5+ 6-7+ 8-9+ 10-11+ 12-13+ 14-15+ 16+
Attacker proficient with weapon	Yes No
Attacker is blind	No Yes
Fighter Progression per level applies	No Yes
Details of Opponent
Armor Type of Opponent	Armor Class adjustment does not apply (e.g. monster not wearing armor) None Shield only Leather or padded armor Leather or padded armor + shield / studded leather / ring mail Studded leader or ring mail + shield / scale mail Scale mail + shield / chain mail Chain mail + shield / splint mail / banded mail Splint or banded mail + shield / plate mail Plate mail + shield
Armor Class of Opponent	10 9 8 7 6 5 4 3 2 1 0 -1 -2 -3 -4 -5 -6 -7 -8 -9 -10
Opponent's AC benefit of shield
Opponent's AC benefit of dexterity
Details of Situation
Range	Melee Short Medium Long
Special Type of Attack	Normal Flank Attack Rear Attack Stunned, prone or motionless opponent Invisible opponent
Attacker is charging	No Yes
Opponent is charging	No Yes
Dungeon Master's Fiat
To hit modifier
Armor class modifier

Calculate!

Notes

This calculator is intended to be a rules as written / by the book calculator for "To Hit" roles of Advanced Dungeons and Dragons 1st Edition. It relies on the Attack Matrix tables as per p74 of the Dungeon Masters Guide (and hence is not based on the Advanced Dungeons and Dragons 2nd Edition THAC0 concept).

Still to implement

• Race/monster modifiers
• Giant and Machine Missiles: no dexterity bonus to armor class (Dungeon Master’s Guide p64)
• Thief backstab surprise bonus
• Spell effects
• Parrying action (Player’s Handbook, p104)
• Using a net underwater (-4, DMG p56)
• Opponent encumbered, held by one leg, off balance, etc +2 (Dungeon Master's Guide p67)
• Opponent cover and concealment adjustments (Dungeon Master’s Guide p64)
• Adjust Special Attack Type rules to only apply to Melee
• Intoxication, moderate -1, Intoxication, great -5 (Fighting Wheel Game Aid)
• Other Weapons detailed in the Fighting Wheel Game Aid
• A
• B

Unanswered questions

• The non-proficiency penalty for weapons is provided per class. What non-proficiency penalty should be applied to non-player characters that do not have a character class?
• To what extent do the situational factors detailed on p67 of the Dungeon Masters Guide stack with those of p70 of the Dungeon Masters Guide? For example, if it is a rear attack against an opponent that is held by one leg, do both +2 modifiers apply?
• What "Combat Ability" means for Typical Inhabitants, as set out in the table on p88 of the Dungeon Masters Guide