The original adventure along the Sword Coast offered a paltry eighty thousand experience, whereas the expansion doubled that number to 161k xp. For a single classed character, that is simply one more level and not really important. For a multiclassed character, it's a big difference that reduces the gap in levels. For a dual classed character, it's a huge opportunity that makes the difference between having to wait until BGII before switching classes or being able to almost catch up right now. The original adventure in Amn offered experience somewhere around two and a half million, whereas the expansion more than tripled the limit to 8,000,000 xp. Given that the first game was released with all expansions, it will be assumed that the second will follow the higher cap as well.

• Baldur's Gate XP cap at 161,000
  
• Warrior and Cleric classes cap at level 9
  
• Wizard classes cap at level 8
  
• Rogue classes and Druid class caps at level 10

• Fighter aspect will be 7
  
• Cleric aspect will be 7
  
• Mage aspect will be 7 (so close to 8!)
  
• Thief aspect will be 8

(Dual classed variants require a whole section for discussion on their own.)

The benefit of playing a single classed character to levels over seven is a matter of personal choice, but most players are skeptical of the benefit a thief protagonist can enjoy when so many NPCs are already decent thieves and the best thief in the game starts your adventure with you. Not to mention the fact that you can almost max skill points around level seven anyways, and most money comes from quests and blatant theft rather than sleight of hand.

The most important thing to remember when rolling a multi-classed character is the racial restrictions placed on your multiclassing options. Also important to note is that class kits can not be selected as either of your multiple classes (gnome illusionist is the only exception). The classes available for multi-class characters are: Fighter, Ranger, Cleric, Druid, Mage, Thief.

Human

• Cannot multi-class at all; may only dual class.

Elf

• No Cleric, Druid nor Ranger combination.
  
• May triple-class as Fighter/Mage/Theif.

Half Elf
[/list]

• Every combination is possible (except Cleric/Thief).
  
• May triple class as Fighter/Mage/Theif.

Gnome

• Any pairing of Fighter, Illusionist, Thief, Cleric.

Halfling

• Fighter/Thief is the only option.

Dwarf

• Fighter/Thief and Fighter/Cleric are the only two options.

Half-Orc

• Any pairing of Fighter, Cleric and Thief.

Humans will always be one class, and while a smart player may take advantage of dual classing human characters, I have yet to notice if an NPC has done that. Elves and half-Elves are a mixed bag and pretty much can do anything. Gnomes don't have to be illusionists, but you're really wasting the point of being a Gnome if you forgo that option. Halflings have a Dex bonus that makes both Fighter and Thief viable, as well as Thief skill point bonuses. Dwarves have a max Dex of 16 and abysmal starting Thief skills that basically say "pick a better Thief race". Also remember that half-Orcs have a Str and Con bonus, without the Dex penalty, which makes them better for both obvious and stealthy fighting.

If you want to play a non-Human and non-Elf character, adhere to racial expectations. If you just want to play more than one class as the same time, look into the (half) Elf option. If you have a lot of patience and want the absolute most benefit from your character, play Human and dual class.

There are a lot of options. A lot of options. You practically have to shake a stick in order to narrow down your options to something that resembles a list to pick from. At least your race is decided. You are definitely Human and you definitely start as just one class. Which brings us to our first group of pro's and con's.

Some classes carry well into a second class while others literally waste abilities. Depending on which order you take your classes, it could go either way. For example, a fighter gains d10 hitpoints and everyone else gets less, so if you spend nine levels in anything other than Fighter then you are losing potential hitpoints.
You must plan ahead to dual class, kind of like growing up always knowing that you want to be a special forces commando and training for basic infantry first. There are stat requirements for each class, and they are exceptionally strict for dual classing. Your primary stat for your first class must be at least 15 and the primary stat for your second class must be at least 17. So you need to be very careful how you allocate your points when rolling for stats, and put your highest stat in the second class's requisite.
Also pay attention to the weapons you will be allowed to use in the second class versus the ones you can use initially; for example, you will lose whatever points you put into non-Cleric weapons when you dual into Cleric. Ranger:Beastmaster will never use metal weapons, ever. Otherwise this restriction is only a problem until you unlock your previous class abilities. You can only backstab with Thief weapons and you can only use one fighting stance at a time, so be mindful of the proficiency that you take with your new class.
The first bit of advice is to immediately check, upon reaching level 2, if you are able to dual into your chosen class. You can cancel out, but it will tell you if you've already made a mistake.

Important Information:
• You can only dual in to and out of Fighter, Cleric, Mage, Rogue and out of their class kits.
  (Ranger and Druid too, but are tricky to set up).
  
• You start in a class kit and Dual into a generic class later.
  
• Dual classing allows use of all proficiency points at both first levels (unless you spend points one the same weapon twice; they overlap, not add).
  
• A Mage can still cast from spell scrolls and wands while wearing Fighter armor.
  
• Warrior classes gain d10 hp until level 9, Rogue and Mage roll dice until level 10.
  
• Constitution bonuses and penalties are retroactive, not permanent at level gain. Fighters gain higher bonus than non-fighters, and bumps back up when you unlock Fighter aspect.
  
• A second class Fighter can put all four proficiency points into one weapon at first level, allowing a grandmaster rating at third level.
  
• The best THAC0 and saves of either class is used, they are not bonuses to be added together (unlike 3rd edition and later rules).
  
• You can increase proficiency specialization if first class was Fighter (despite the rules, manual, and common sense dictating otherwise). *works with multi-class leveling up non-fighter class, not tested with dual class*

At the point you switch classes, you lose whatever experience you had gained towards your next level in the old class. Unused experience does not carry over, so dual class as soon as you reach your last level in the old class. You can only dual into the archtype classes of Fighter, Cleric, Mage and Thief. Ranger can only pair with Cleric and Druid with only Fighter. Depending on what bonuses and abilities you want to end up with, and if you're going to import into BGII later, you will level up only so far and with certain classes in a specific order.

Starting as Warriors
• Improves THAC0 every level by one, including first level!
  
• Gains proficiency every third level.
  
• Can gain Grand Mastery at level 9 if a weapon started as specialized (plus two points elsewhere) or can Master (+3 to hit and damage) two weapons at level 6 (plus two points elsewhere).
  
• Gains +1/2 attack at levels 7 and 13.
  
• Regains extra attacks from specialization after unlocking Fighter aspect.
  
• Stops gaining d10 hit points at level 9 (max 90 without Con bonus).
  
• Forever have access to all armors and weapons (except if dual into Cleric).
  
• Needs high Charisma if you go into Druid.

Starting as Clerics
• Improves THAC0 by two every third level. (THAC0 18 at level 3, 16 at level 6, et cetera)
  
• Gains proficiency every fourth level.
  
• Gains access to spell tiers at levels 3, 5, 7, 9, 11, 14. Wisdom of 17 and 18 gives bonus spells up to tier 3.
  
• Stops gaining d8 hit points at level 9 (max 72 without Con bonus).
  
• Forever have access to Cleric specific gear, but may use non-Cleric weapons afterwards.
  
• Must meet abnormally restrictive stat requirements (Str13, Dex13, Con15 (actually 17), Int8, Wis14 (actually 15), Chr8) if going into Ranger.

Starting as Mages
• Improves THAC0 by one every three levels: 4, 7, 10, 13, et cetera.
  
• Gains proficiency every sixth level.
  
• Gains access to spell tiers every odd level except level 11. Continues every other level from 12.
  
• Five available spell slots of (almost) all accessible tiers at level 15; Four for most tiers at level 12.
  
• Stops gaining d4 hit points at level 10 (max 40 without Con bonus).
  
• Forever have access to Mage specific gear, including ability to cast scrolls and wands in armor.

Special Note: A specialist Mage can dual class (out) only if you meet second prime stat requirement in addition to all other class and stat requirements.
• Abjurer Wisdom 15
  
• Conjurer Constitution 15
  
• Diviner Wisdom 16
  
• Enchanter Charisma 16
  
• Illusionist Dexterity 16
  
• Invoker Constitution 16
  
• Necromancer Wisdom 16
  
• Transmuter Dexterity 15
  *Wild Mage cannot dual class.

Starting as Thieves
• Improves THAC0 by one every odd numbered level.
  
• Gains proficiency every fourth level.
  
• Improves backstab multiplier at level 5, 9, and 13. Maximum multiplier at level 13. (Specific Thief kits may vary these numbers. Swashbuckler cannot backstab at all.)
  
• Will maximize all Thief skills around level 25 (depending on kit); and can effectively maximize (95%) Pick Locks and Find Traps before level 8 (depending on kit, Dex and equipment).
  
• Swashbuckler gains +1 to armor, hit and damage at levels 6 and 11.
  
• Bounty Hunter gains a Hold Person trap at level 11.
  
• Stops gaining d6 hit points at level 10 (max 60 without Con bonus).
  
• Forever have access to detect traps in any armor (without helmet), and all Thief abilities in Studded Leather (or lighter) armor.
  
• Forever have access to backstab(!) with Thief standard weapons (includes Katana and Staff!) as long as hiding in shadows first (use Invisibility spell/potion for guaranteed stealth).

Starting as Ranger
• Your choice is limited specifically to Ranger/Cleric.
  
• Limited to Good alignments.
  
• Archer kit provides +1 to hit and damage with ranged weapons, but cannot specialize to grandmaster in sling, thereby wasting the points spent on other weapons when switching to Cleric.
  
• Stalker kit's backstab uses Thief weapons, of which only Quarterstaff can be used by Clerics.
  
• Beastmaster's weapon restrictions really hurt your choices as a Cleric. You will not be able to wield restricted weapons despite being allowed to select them for weapon proficiency.

Starting as Druid
• Your choice is limited specifically to Fighter/Druid.
  
• Limited to only True Neutral alignment.
  
• Needs 15+ in both Wisdom and Charisma if going into Fighter.

Now that you've gone to the trouble of advancing your character a couple of levels and picked what abilities you cannot live without, there is some information that you should know about concerning the experience cap of Baldur's Gate. There is also some discussion helpful to deciding when those abilities are as good as they aught to be or if they should be a few points higher before switching over.

In order to pass your previous class's level as your new class, refer to this handy list:
• Starting as a Warrior and then Dual classing into anything other than Cleric, stop at level 7 (stop at 6 if going into Cleric).
  
• Same advice for Ranger going into Cleric; stop at level 6.
  
• Starting as a Cleric and then Dual classing into Mage or Thief should stop at level 7; stop at level 6 for all other combinations.
  
• Starting as a Druid can go all the way to level 7 before Dual classing to Fighter.
  
• Starting as a Mage and then Dual classing into Fighter or Cleric then stop at level 6, and stop at level 7 if going into Thief.
  
• Starting as a Thief (or planning for Imoen) and Dual classing into Mage or Cleric then stop at level 7 (otherwise you'll tie at level 8, which might be okay if you're importanting to BGII), and stop at level 6 if going into Fighter.

The highest level in Baldur's Gate II is 40, but some classes will not reach that level even if pure and others will not reach it unless pure. To reach the highest level possible after exporting to Baldur's Gate II, refer to this handy list:

Starting as a Warrior
• Stop at level 12 for Cleric.
  
• Stop at level 10 for Druid.
  
• Stop at level 9 for Mage. *
  
• Stop at level 14 for Thief.

Starting as a Ranger **
• Stop at level 11 for Cleric.

Starting as a Cleric
• Stop at level 9 for Fighter.
  
• Stop at level 8 for Ranger. *
  
• Stop at level 9 for Mage. *
  
• Stop at level 15 for Thief.

Starting as a Druid
• Stop at level 11 for Fighter.

Starting as a Mage **
• Stop at level 10 for Fighter.
  
• Stop at level 12 for Cleric.
  
• Stop at level 14 for Thief.

Starting as a Thief
• Stop at level 11 for Fighter.
  
• Stop at level 14 for Cleric.
  
• Stop at level 11 for Mage. *

* You will not reach level 39 as a Mage nor Ranger. These suggested numbers are for the highest level possible otherwise.
** You might as well Dual class because you're not going to get past level 31 anyways.

The two short answers are High Level Abilities and spending half the game being useless. A character loses all their abilities until the new class exceeds the old class in level. The higher the level then the more time spent being useless. At different levels near 20, classes offer High Level Abilities that dramatically improve their power. You gain more as you advance every few levels, until you start gaining them every level as you reach closer to level 40. Some other reasons are listed here:

• Warrior classes are the only class that maxes THAC0 reductions at level 19. But having a THAC0 of 1 or 0 is merely a semantic for modifying to-hit calculations. If you really need the extra probablity to hit, then you probably have other bonuses already.
  
• Warriors gain +1/2 attack at levels 7 and 13, but it simply stops there.
  
• Fighter's Grand Mastery in a weapon can be obtained by level 9 compared to being able to use many other weapons poorly (in comparison).
  
• A Thief has x4 backstab at level 9 (Ranger:Stalker has x3 at same level) which is plenty enough damage if you use the right equipment.
  
• Picking pockets is pointless with the multitudes of gold available in the game. Finding traps is checked every round, so it needn't be maxed out. Lockpicking can be boosted with potions so it needn't be maxed either. Hiding in Shadows and Moving Silently have equipment that improves them, and invisibility will guarantee success. The community's consensus is that 9 levels of rogue is all you need to be wildly successful, when supported by a party.
  
• Despite all the spells available, you can only cast one spell per round. If you really want to circumvent that mechanic, then start as something else and Dual into Mage.
  
• The maximum number of spells for any spell level is 5 (arcane) and 9 (divine); higher levels do nothing to improve this situation whereas bonus spell slots (equipment and Wisdom) are immediately effective.

Things to remember when choosing your Multi Class and Dual Class combinations that may help to narrow your choices to how you'd like to play the game. Pick cohesive combinations for greater chances of success and pick contradictory combinations for challenges and competitions.

No class offers more hitpoints, nicer armor, nor better THAC0. Because hit points are so limited and important, the game's "normal mode" simply gives you the maximum. Your THAC0 will never improve because it is already so good. Warriors are the only class that innately gain additional attacks, but the bonus ends relatively early; so switching out is better long term than switching in if you're Dual Classing.

Access to heavy armor with the second best hit points and THAC0 in addition to divine spells, makes starting or multi-classing as a Cleric hard to turn down. The kits have zero disadvantages, so if you're going to Dual Class with a good alignment anyways, then the +1 attack from Lathander's Boon is on par with a Fighter's extra attacks. The only real downside is not being able to use pointy weapons and having almost 20 fewer hitpoints at level 9.

There are more rogues in the game than any other class by an order of magnitude. You even start the game with the best Thief in the game, Imoen. The first road you walk also gives you a fighter/thief to recruit. It is exceptionally important to have a Thief in the party, but there are several reasons why the protagonist should not be one. Rolling d6s means less hitpoints than Clerics (by 14 points at level 10), but this is actually an issue because a lack of good armor. Backstabing only occurs in melee, which means your protagonist is even more likely to get attacked. Traps at low levels means not putting points in abilities that can be used infinitely. You'll want at least one Thief around, just don't Dual Class as one yourself. Multi-class Thieves are an entirely different story, and even mitigate the divided experience effect.

Hit points for your protagonist will never be worse unless you play hard mode and get super unlucky rolls at level up. You will be able to use scrolls and wands (in armor too), but those hitpoints will never be replaced. Your spell slots are bound specifically to level, unlike Clerics who can benefit from Wisdom immediately. On the plus side, your THAC0 is guaranteed to improve and you can advance pretty quickly as a Mage due to the low experience requirements at lower levels. When Dual Classing, it is infinitely advisable to start elsewhere. When multi-classing, it is advisable to pair with Warrior or Cleric.

The exception is Druid and Ranger, which include other abilities that make it okay. Clerics are already decent combatants, so the benefits of combining with Fighter are blunted significantly. Basically everything good to say about Fighters, you can say with almost as much conviction about Clerics. Clerics have divine spells and can turn Undead, whereas Fighters have the best innate stats (saves, THAC0, Damage, weapons) and are good against everything. Consider those two factors when deciding between these two classes, but never compromise by taking them both.

A challenge combination is Cleric and Thief. It's plenty viable, but weapon choices make it exceptionally limited in melee combat and Backstabing is limited to quarterstaves. You can realize this combination as a half Orc for extra fun.

The half Orc Fighter/Thief can have 19 Str and Con, without the Dexterity penalty and abysmal Thief Skills that Dwarfs suffer from. Sure strength is calculated after the backstab multiplier (unlike the pen and paper rules), but being able to reliably land a backstab is way better than commonly missing. If you're going to multi-class with a Thief anyways, go this route.

A Fighter/Mage is an awesome combination that combines two extremes. You get almost as many hitpoints as a Cleric (more with high Constitution) but have access to Arcane spells, scrolls, and wands. If you Dual Class from Fighter to Mage, then you benefit from the most important Fighter abilities (grand mastery of any one weapon and +1/2 attack, THAC0, HP, equipment) and may still unlock access to the most powerful Mage abilities too.

Prove it. Provide comments that describe what I got wrong and how it is wrong. Describe in detail what is correct so that I can improve this guide. But most importantly, I won't believe you unless I can reproduce the claim myself. I believe that Wild Mages should be able to Dual Class but I haven't gotten it to work yet, so I'm saying that they can't. I hope somebody can prove me wrong there.

These kinds of changes are not likely to change this guide, but some features are obviously bugs (such as being able to put all four starting points into one weapon when Dual Classing into Fighter) and I hope they do get fixed even though it will mean a more difficult game for me. I will update the guide however patch notes describe the changes.

If you don't like my guide because you have poor reading comprehension skills, then please keep that information to yourself. If you think a certain section should be written differently to be more clear, then I'm open to fixing those issues. If you just want to rain praise upon me for bringing this information together, then thanks. I'm only doing it for my U/D ratio, but kudos are still appreciated.