I think at some point it could just be a dm ruling, like do they allow you to have 17 ac plus wis.
A DM could "rule" anything, that doesn't change the fact that deciding a Tortle Monk's unarmored AC is 17 + Dex is absolutely a homebrew that is not supported by the rules. They're quite explicit about calculating AC.
No Strength, Dexterity, Constitution, Wisdom, Intelligence or Charisma bonus if you have a set "Base AC".
Additionally, if you are a 1st level Barbarian and multiclass into Monk you ONLY get the Barbarian AC Calculation. PHB 165 states "if you already have unarmored defense feature, you cannot gain it again from another class". Fortunately for races with unarmored defense, they aren't acquiring it from a "class" so they can technically choose the source.
I have NO idea where this "you can choose your AC" comes from, because PHB says nope. It might be something like "if you cast mage armor on someone in plate armor, you can't reduce their AC" but I see a lot of this AC calculation error on the web.
Your Armor Class (AC) represents how well your character avoids being wounded in battle. Things that contribute to your AC include the armor you wear, the shield you carry, and your Dexterity modifier. Not all characters wear armor or carry shields, however.
Without armor or a shield, your character’s AC equals 10 + his or her Dexterity modifier. If your character wears armor, carries a shield, or both, calculate your AC using the rules in the Equipment section. Record your AC on your character sheet.
Your character needs to be proficient with armor and shields to wear and use them effectively, and your armor and shield proficiencies are determined by your class. There are drawbacks to wearing armor or carrying a shield if you lack the required proficiency, as explained in the Equipment section.
Some spells and class features give you a different way to calculate your AC. If you have multiple features that give you different ways to calculate your AC, you choose which one to use.
I have NO idea where this "you can choose your AC" comes from, because PHB says nope. It might be something like "if you cast mage armor on someone in plate armor, you can't reduce their AC" but I see a lot of this AC calculation error on the web.
Mage Armor says "You touch a willing creature who isn't wearing armor," so you can not cast mage armor on someone in plate. It isn't the caster you decides the AC it is the creatue that decides there own AC. If you can not cast mage armor on a monk to reduce their AC as the monk can then decide whether to use the mage armor calculation or the unarmored defence (and will presuimably choose the one with the higher calculation.
The Sage Advice Compendium also has an official ruling reiterating how AC calculation work;
How do you calculate a creature’s Armor Class (AC)? Chapter 1 of the Player’s Handbook (p. 14) describes how to determine AC, yet AC calculations generate questions frequently. That fact isn’t too surprising, given the number of ways the game gives you to change your AC! Here are some ways to calculate your base AC:
Unarmored: 10 + your Dexterity modifier.
Armored: Use the AC entry for the armor you’re wearing (see PH, 145). For example, in leather armor, you calculate your AC as 11 + your Dexterity modifier, and in chain mail, your AC is simply 16.
Unarmored Defense (Barbarian): 10 + your Dexterity modifier + your Constitution modifier
Unarmored Defense (Monk): 10 + your Dexterity modifier + your Wisdom modifier.
Draconic Resilience (Sorcerer): 13 + your Dexterity modifier.
Natural Armor: 10 + your Dexterity modifier + your natural armor bonus. This is a calculation method typically used only by monsters and NPCs, although it is also relevant to a druid or another character who assumes a form that has natural armor.
These methods—along with any others that give you a formula for calculating your AC—are mutually exclusive; you can benefit from only one at a time. If you have access to more than one, you pick which one to use. For example, if you’re a sorcerer/monk, you can use either Unarmored Defense or Draconic Resilience, not both. Similarly, a druid/barbarian who transforms into a beast form that has natural armor can use either the beast’s natural armor or Unarmored Defense (you aren’t considered to be wearing armor when you use natural armor). What about a shield? A shield increases your AC by 2 while you use it. For example, if you’re unarmored and use a shield, your AC is 12 + your Dexterity modifier. Keep in mind that some AC calculations, such as a monk’s Unarmored Defense, prohibit the use of a shield. Once you have your base AC, it can be temporarily modified by situational bonuses and penalties. For instance, having half cover gives you a +2 bonus to your AC, and three-quarters cover gives a +5 bonus. Spells sometimes modify AC as well. Shield of faith, for example, grants a target a +2 bonus to AC until the spell ends. Magic items can also enhance your AC. Here are a few examples: +1 chain mail gives you an AC of 17, a ring of protection gives you a +1 bonus to AC no matter what you’re wearing, and bracers of defense grant you a +2 bonus to AC if you’re not wearing armor or using a shield.
So I’m having an issue where my monk tortle is staying at 17 ac when he has a 10+5ws+4dex unarmored. He has nothing equipped at all, so is there a way to fix his ac on DnD beyond?
So I’m having an issue where my monk tortle is staying at 17 ac when he has a 10+5ws+4dex unarmored. He has nothing equipped at all, so is there a way to fix his ac on DnD beyond?
If you open your character sheet on the DnDBeyond site you can click on your AC to see how it is calculated. Just below where it shows how the AC is calculated it will say "Customize", if you click on this it will expand out the customization tab and give you four different ways of modifying your AC. You can then use any of these to modify your AC until you get the correct value of 19.
Personally I would just add a 2 miscellaneous bonus to your AC or override the base AC plus dex to be 12, the fourth and second options respectively, as these seem least likely to cause problems with DnDBeyond handling any AC boost magic items you may get.
I think at some point it could just be a dm ruling, like do they allow you to have 17 ac plus wis.
A DM could "rule" anything, that doesn't change the fact that deciding a Tortle Monk's unarmored AC is 17 + Dex is absolutely a homebrew that is not supported by the rules. They're quite explicit about calculating AC.
No one said dex, we said wis or con.
No Strength, Dexterity, Constitution, Wisdom, Intelligence or Charisma bonus if you have a set "Base AC".
Additionally, if you are a 1st level Barbarian and multiclass into Monk you ONLY get the Barbarian AC Calculation. PHB 165 states "if you already have unarmored defense feature, you cannot gain it again from another class". Fortunately for races with unarmored defense, they aren't acquiring it from a "class" so they can technically choose the source.
I have NO idea where this "you can choose your AC" comes from, because PHB says nope. It might be something like "if you cast mage armor on someone in plate armor, you can't reduce their AC" but I see a lot of this AC calculation error on the web.
https://www.dndbeyond.com/sources/basic-rules/step-by-step-characters#ArmorClass
Armor Class
Your Armor Class (AC) represents how well your character avoids being wounded in battle. Things that contribute to your AC include the armor you wear, the shield you carry, and your Dexterity modifier. Not all characters wear armor or carry shields, however.
Without armor or a shield, your character’s AC equals 10 + his or her Dexterity modifier. If your character wears armor, carries a shield, or both, calculate your AC using the rules in the Equipment section. Record your AC on your character sheet.
Your character needs to be proficient with armor and shields to wear and use them effectively, and your armor and shield proficiencies are determined by your class. There are drawbacks to wearing armor or carrying a shield if you lack the required proficiency, as explained in the Equipment section.
Some spells and class features give you a different way to calculate your AC. If you have multiple features that give you different ways to calculate your AC, you choose which one to use.
Mage Armor says "You touch a willing creature who isn't wearing armor," so you can not cast mage armor on someone in plate. It isn't the caster you decides the AC it is the creatue that decides there own AC. If you can not cast mage armor on a monk to reduce their AC as the monk can then decide whether to use the mage armor calculation or the unarmored defence (and will presuimably choose the one with the higher calculation.
PHB 165
"if you already have unarmored defense feature, you cannot gain it again from another class"
The Sage Advice Compendium also has an official ruling reiterating how AC calculation work;
Yes, "unarmored defense" specifically stops you getting it again. But apart from that you get to pick and choose.
So I’m having an issue where my monk tortle is staying at 17 ac when he has a 10+5ws+4dex unarmored. He has nothing equipped at all, so is there a way to fix his ac on DnD beyond?
If you open your character sheet on the DnDBeyond site you can click on your AC to see how it is calculated. Just below where it shows how the AC is calculated it will say "Customize", if you click on this it will expand out the customization tab and give you four different ways of modifying your AC. You can then use any of these to modify your AC until you get the correct value of 19.
Personally I would just add a 2 miscellaneous bonus to your AC or override the base AC plus dex to be 12, the fourth and second options respectively, as these seem least likely to cause problems with DnDBeyond handling any AC boost magic items you may get.
Thank you for the advice