How strong or large does a character have to be to wield a two-handed weapon one-handed?

The rules don't allow wielding a two-handed weapon with one hand, regardless of your strength score or effects that increase your size. Anything outside of the rules is up to the DM.

Yes, 5e does away with much of the complexities of weapon sizes, essentially reducing it to disadvantage for using weapons of larger creatures.

The DMG, (Page 278) says, 'A creature has disadvantage on attack rolls with a weapon that is sized for a larger attacker.'

But there are no rules governing it the other way. A human doesn't get advantage on a halfling's dagger, for example. And there's no way of using a greatsword one handed - even if it was a halflings greatsword, the halfling would simply have disadvantage for using a heavy weapon.

It wouldn't take much to redo weapon sizes to account for this.

Every weapon has a size: tiny, small, medium, large, huge. A figure can dual-wield (size-1 or smaller) weapons, single-hand (same size) weapons, two-hand (size+1) weapons, and cannot wield (size+2 or bigger) weapons. 

Weapons that currently have the tag "light" could be tiny; ones with the tag "versatile" could be medium; ones with the tag "large" could be large. Some weapons (bows for example) could be "two-handed" regardless of their size.

Two handed weapons typically have the quirk that they aren't actually all that heavy.  The issue with using a two handed weapon one handed has more to do with leverage and balance than raw strength (even a super strong human is going to have issues wielding that great-sword in one hand).  A single handed weapon is balanced in mind with using it in one hand a two-handed weapon is balanced in mind with using two (keep in mind a lot of stress is put on the wrists for a poorly balanced weapon).

Size would make the bigger difference however.  A larger creature could likely use a two handed weapon because they have the larger forearms and hands to support the different leverage and compensate the balance, essentially making it a one handed weapon relative to their size.  It still wouldn't be a great for them as a weapon specifically designed and balanced to be one handed for their larger stature but they could manage it.

Quote from Loswaith >>

Two handed weapons typically have the quirk that they aren't actually all that heavy.  The issue with using a two handed weapon one handed has more to do with leverage and balance than raw strength (even a super strong human is going to have issues wielding that great-sword in one hand).  A single handed weapon is balanced in mind with using it in one hand a two-handed weapon is balanced in mind with using two (keep in mind a lot of stress is put on the wrists for a poorly balanced weapon).

Size would make the bigger difference however.  A larger creature could likely use a two handed weapon because they have the larger forearms and hands to support the different leverage and compensate the balance, essentially making it a one handed weapon relative to their size.  It still wouldn't be a great for them as a weapon specifically designed and balanced to be one handed for their larger stature but they could manage it.

 I think, my question tied into the photos I have seen, like the recent one of the guest character on Critical Role: "Keg." Both her weapons, although I believe are simply a battle axe and war hammer, the handles are longer than her body...I do not know how to link the image. No big deal, just thought I would ask. Thank you all.

The original books do not allow it, as started rule above. However looking at the new classes such as Goliath who have "Powerful Build. You count as one size larger when determining your carrying capacity and the weight you can push, drag, or lift." They could easily use 2 handed weapons in one hand since they lift and carry as a large size. Such as a Minotaur who has a large 2 handed great axe doing double what the medium size Great axe does... "Greataxe. Melee Weapon Attack: +6 to hit, reach 5 ft., one target. Hit: 17 (2d12 + 4) slashing damage."  Some books now even have a Minotaur class..... not to mention if you enlarge yourself you could pick up the Minotaur's great axe and use it then. There are tons of rules and they already have a bunch of overlapping issues. WotSC has done a poor job on some of the rules which is why your DM has to wade through the Chaos to find what works for you. Like the "critical hit" only doubles the die roll yet every monsters damage has the modifiers in there to double? idiotic.

Quote from Scorp28 >>

The original books do not allow it, as started rule above. However looking at the new classes such as Goliath who have "Powerful Build. You count as one size larger when determining your carrying capacity and the weight you can push, drag, or lift." They could easily use 2 handed weapons in one hand since they lift and carry as a large size. Such as a Minotaur who has a large 2 handed great axe doing double what the medium size Great axe does... "Greataxe. Melee Weapon Attack: +6 to hit, reach 5 ft., one target. Hit: 17 (2d12 + 4) slashing damage."  Some books now even have a Minotaur class..... not to mention if you enlarge yourself you could pick up the Minotaur's great axe and use it then. There are tons of rules and they already have a bunch of overlapping issues. WotSC has done a poor job on some of the rules which is why your DM has to wade through the Chaos to find what works for you. Like the "critical hit" only doubles the die roll yet every monsters damage has the modifiers in there to double? idiotic.

 

 

 Okay, so, in me and my friends campaign, I just managed to get a blessing that's going to turn my itty bitty, LVL 8,  2'8'' Kobold Monk, into a 21ft, +6 STR, 7700lbs behemoth, with all her weapons and current gear scaled up with her. 

    So....what the hell do we do? What happens to my weapons damage? My hit dice? Base speed? My DM and I have no idea, but due to how stupid, dumb and hilarious we found it, he's already said he wants to make this permanent in some way. Whether he downgrades my size to Large instead of Huge permanently, makes it a transformation I can use so many times a day, or whatever he wants to do with it, we could use some help figuring out the logistics.

So, by RAW.   My Orc has no easier time using his greataxe now (with a 24 strength) than he did when he started (with a 14 strength).   Makes zero sense.

I mean, the orc hits the same target with it 25% more often and does 5 more damage... so if that isn't any better then... well, maybe you're looking for a different game system.

My point is that if your strength is 14 and you can hold a weapon in two hands, then if your overall strength is increased by 10 you should have the strength to use it in one hand.

I'd say that two-handed weapons are constructed so that you need 2 hands in order to wield them properly at all. But I could see a DM allowing your very stronk Orc to wield that battleaxe 1-handed... at disadvantage. Which having an extra 10 to your Strength score almost makes up for.

Edit: Or, make it count as an improvised weapon, so you don't normally get proficiency.

Yeah, a two handed weapon is two handed because of its purpose, not because of your strength.

Yeah I'd just treat it as an improvised weapon. 

"An improvised weapon includes any object you can wield in one or two hands, such as broken glass, a table leg, a frying pan, a wagon wheel, or a dead goblin."

Any object.

Then, because we're now firmly in RAW = Whatever the DM decides territory. I'd set the damage die to what is reasonable for a one hander, a d8. And you're not getting proficiency on the attack unless you otherwise normally get proficiency on improvised weapons.

Heavy weapons aren't that heavy. I mean, they're not so heavy that you couldn't easily pick one up in one hand with the lowest possible Strength score at level 1. That's never been the issue.

It's a game mechanics thing wearing the face of a realism thing. Don't overthink it.

Quote from ChoirOfFire >>

Heavy weapons aren't that heavy. I mean, they're not so heavy that you couldn't easily pick one up in one hand with the lowest possible Strength score at level 1. That's never been the issue.

It's a game mechanics thing wearing the face of a realism thing. Don't overthink it.

 Maybe not too heavy to lift, but liable to throw you off-balance when wielding if they're longer than you're tall and/or weigh a good percentage of your body weight, hence why Small races wield them at disadvantage.

To put it a different way, a character strong enough to pick up and wield what others call a two-handed weapon with one hand isn't using a greatsword, they're using a longsword with one hand. 

If you want to argue that a character should be able to become strong enough to use the weapon one handed without it doing less damage than if they used it two handed, that seems absurd.

Quote from Lunali >>

To put it a different way, a character strong enough to pick up and wield what others call a two-handed weapon with one hand isn't using a greatsword, they're using a longsword with one hand. 

If you want to argue that a character should be able to become strong enough to use the weapon one handed without it doing less damage than if they used it two handed, that seems absurd.

 That is a somewhat elegant solution. The weapon would in some respects become versatile. With the Great Axe example, two-handed it would be 1d12 but one-handed it would be 1d10.

Quote from Wysperra >>

Quote from Lunali >>

To put it a different way, a character strong enough to pick up and wield what others call a two-handed weapon with one hand isn't using a greatsword, they're using a longsword with one hand. 

If you want to argue that a character should be able to become strong enough to use the weapon one handed without it doing less damage than if they used it two handed, that seems absurd.

 That is a somewhat elegant solution. The weapon would in some respects become versatile. With the Great Axe example, two-handed it would be 1d12 but one-handed it would be 1d10.

1d8. One handed weapons do at most 1d8.