How does haste interact with the heavy armor penalty?

For a character that is wearing heavy armor, but does not have the prerequisite strength, there is a 10ft speed penalty.

If the Armor table shows “Str 13” or “Str 15” in the Strength column for an armor type, the armor reduces the wearer’s speed by 10 feet unless the wearer has a Strength score equal to or higher than the listed score.

Haste doubles the speed of the person it was cast on.

Until the spell ends, the target’s speed is doubled

Since the movement speed of heavy armor is a fixed amount, does the doubling apply to the base speed or the current speed? Eg. A human with a base speed of 30. They put on heavy armor and have their speed reduced to 20. Haste is cast on them, does their speed become 30×2 - 10 = 50 or (30-10)×2=40?

• Sep 8 '20 at 20:59

Their speed becomes 40

The general rule for speed/movement begin by stating:

Every character and monster has a speed, which is the distance in feet that the character or monster can walk in 1 round.

A weak character wearing heavy armor with 30 feet of movement has its speed reduced by 10 feet, which means its speed becomes 20 feet. This is the attribute that is then Doubled by a casting of Haste, resulting in a final speed of 40 feet.

Haste does not double the speed of 30 because the character does not have 30 feet of movement (ie a speed of 30) when the spell affects them.

• Is there anything in the rules that substantiates this order of operations? If the person had Haste cast on them, then put on the armor (very quickly), would they instead move 50 feet per round? Or if they put on and off a Girdle, would their speed go to 50 then back to 40, or to 60 then back to 50?
– Yakk
Sep 9 '20 at 12:45
• @yakk I suspect that the rules for donning/doffing armor were intended to be longer than a typical combat, in part, to prevent some of these kinds of issues. You're talking about a pretty edge case. I think that if a table runs into a situation where a player is attempting (and able) to don/doff armor while affected by Haste, that it would require some DM interpretation/adjudication. Sep 9 '20 at 17:47
• Personally, if the player is trying to game that difference of 10' of movement in such a tortuous manner, I would be inclined adhere to the logic that my answer and Please Stop Being Evil's answer posit: Order of application determines the character's speed. To wit: doubling from Haste first, then subtract 10 after the armor is donned under while Haste is still active for net 50 movement. D&D is not a physics simulator and I tend to rule in favor of the players. Sep 9 '20 at 18:00
• So, to be clear, you (a) have no rules text support for your position, and (b) hadn't thought how your ruling handles corner cases, and now that you have you think the other answer does a better job of solving this problem?
– Yakk
Sep 9 '20 at 23:34
• @Yakk. Ouch. Easy, mate. Not sure why you feel you need to belittle. (a) I quoted what I think is the relevant rules text in my answer. (b) The question is about casting haste on weak character in heavy armor. This I answered. You asked about a different scenario which I said I'd apply the same logic to. (c) That logic, as I stated, also happens to align with that of a different answer. Sep 10 '20 at 0:04

It depends on what order the modifiers are applied in

Generally, the order of operations for modifiers is the order in which they are applied. There's no set rule on this, though; you could instead follow the order typically used in arithmetic or make up your own exotic order and use that without violating any written rules for this.

Assuming that typical convention holds:

A creature with a 30' speed who receives the benefits of haste and then dons armor has a speed of 50'.

A creature with a 30' speed who dons armor and then receives the benefits of haste has a speed of 40'.

Either creature would increase in speed to 60' upon doffing the armor, or decrease in speed to 20' upon haste ending.

• Only one of those cases are relevant, it takes 10 minutes to don heavy armour (PHB 146), and haste only lasts for 1, so you can't be hasted first. Sep 8 '20 at 21:07
• @Someone_Evil You could be hasted moments before buckling the last clasp of your breastplate. Hypothetically. Sep 8 '20 at 21:15
• @Someone_Evil That's a weird epistemology, but ok. Here's a third-party spell that makes that case relevant for you, if that helps. Sep 8 '20 at 21:37
• Perhaps more likely a test case is someone who was already in heavy armor and then used magic to change their strength above or below the point at which they received a movement penalty. That could easily be done either before or after the application of haste. A coherent system might be one in which changing strength and then changing back would result in the same number as before rather than a different one.
– Kirt
Sep 8 '20 at 22:10
• @Kirt one example of this in official rules is just the gauntlet's of ogre power. You have to wear them to gain the flat 19 Strength, so taking them off could drop you below the Strength requirement. Sep 9 '20 at 12:32

When multiple effects happen at the same time, the rule in 5e is that the creature whose turn it is picks the order.

I'd apply that to these continuous effects. As movement happens on a creature's turn, they can pick which order movement effects apply.

Then, assuming they want to go fast, the over armored charzcter moves 50' while hasted and in armor too heavy for their strength (assuming 30' base speed).

I can find no other rules guidance for resolving this other than this.

Quote from XGTE:

If two or more things happen at the same time on a character or monster’s turn, the person at the game table — whether player or DM — who controls that creature decides the order in which those things happen. For example, if two effects occur at the end of a player character’s turn, the player decides which of the two effects happens first.

It isn't a perfect fit, but the closest rules advice I can find.

• In what situation do the casting of haste and the penalty from heavy armor happen at the exact same moment? Sep 10 '20 at 0:06
• It seems to me that the reduction to a character's movement as a result of wearing armor they're not strong enough to wear normally is not happening at the same time as the spell Haste being cast on that character. Their effects are concurrent but they are not simultaneous in the way the cited rule is using the term. It seems to focus on when the start/instance of occurrence with two effects. I don't think it's unreasonable for a DM to rule that the player gets to choose, but then, that would be Rule 0. Sep 10 '20 at 0:08
• @thomas Haste modifies your speed continuously, as does wearing too-heavy armor. "Until the spell ends" describes effects that happen during the duration of the spell, not effects that occur when the spell is cast. Compare a fireball to a wall of flame or healing spirit; when the wall of flame or a healing spirit is cast doesn't change the sequence of it burning/healing people.
– Yakk
Sep 10 '20 at 0:11
• @ryk fair enough: I am simply looking for sequencing rules in the actual rules text, and this is the closest I found.
– Yakk
Sep 10 '20 at 0:12
• If I’m already penalized by heavy armor, how can I choose to have haste applied first? The heavy armor penalty has already been applied when haste is effected. Sep 10 '20 at 0:14