Part of an ongoing series of 5e Rules notes.

If we all remember the Golden Rule of D&D Rules — This Is Not A Physics Simulator — then the weirdities of how 5e runs “Size” will … be a little less weird.

Let’s Start with a Table!

Size	Space	Example	HD
Tiny	2.5 x 2.5 feet (4/sq)	Imp, Sprite	d4
Small	5 x 5 feet (1 sq)	Giant Rat, Goblin, Halfling, Gnome	d6
Medium	5 x 5 feet (1 sq)	Orc, Werewolf, Human, Elf, Dwarf, Dragonborn	d8
Large	10 x 10 feet (2×2 sq)	Hippogriff, Ogre	d10
Huge	15 x 15 feet (3×3 sq)	Fire Giant, Treant	d12
Gargantuan	20 x 20 feet (4×4 sq) or larger	Kraken, Purple Worm	d20

So that shows all the size categories, the space they take up on a battle map grid, and some examples, as well as what, in general, their Hit Dice look like.

Most Player Characters are Medium in size — though some races drop down to Small, and a couple of outliers are Large.

How About Some Pictures?

Yes, that’s straight out of the book, but it is so pretty. I will take it down if Hasbro asks me to.

Size and Space

The space described in the table above is that personally controlled by the creature. A human is not actually 5×5 feet, but effectively occupies that space, and rules on passing into or through space apply to all squares so controlled.

You can pass through an enemy creature’s occupied space (ducking past them, under their legs, etc.) if you are 2+ sizes smaller than them. Note that it’s still considered Difficult terrain (double cost), and if you continue on past their reach they will get an Opportunity Attack. So Halflings can duck past an Ogre this way, while Humans could dodge around a Fire Giant’s legs.

Note also that some creatures (typically those larger than Medium) may have physical melee attack reach of more than the normal five feet.

Surrounded!

Spaces taken by creatures cannot overlap. That means, for example, if you as a Medium humanoid are surrounded by enemies, how many enemies that is depends on their size. You could be surrounded by eight Medium enemies, but only four Large enemies could surround you. Similarly while you and your Medium friends could surround a Medium Orc with only eight of you, that Large Ogre would need to be surrounded by twelve Medium opponents.

Line of Sight and Cover

Larger creatures are obviously bigger targets. Assuming you are playing on a square grid, then if you can draw an unobstructed straight line between

any corner/vertex of one creature’s space on the grid map and
any corner/vertex of another creature’s space,

then there is line of sight and each creature can potentially see each other.

In considering cover, pick any corner/vertex of the attacker’s space, and draw lines to the corners of any single square the target occupies.

If 1-2 of those lines are obstructed by something, then the target has half-cover;
if 3 or more are obstructed but you still have line of sight, then the target has three-quarter cover.

(Obviously, a Huge target will have a lot more single squares hanging out there unprotected.)

(Yes, that’s another beautiful drawing from the official books.)

Grappling and Shoving

You only grapple something no more than 1 size larger than you. When grappling, your speed is halved unless the grappled creature is 2+ sizes smaller than you.

Thus, as a Medium Human, you could grapple an Ogre, but not a Treant. Similarly, an Ogre could grapple a Halfling and move off with them at full speed.

You can also only try to Shove something no more than 1 size larger than you.

Getting Small

A creature can squeeze into a space one size category smaller. So a Large creature could squeeze through a 5 ft square opening or 5 ft wide corridor.

When doing so, it counts as Difficult terrain (double movement cost), and the squeezing-through creature has Disadvantage for attacks and Dex saving throws, and attackers have Advantage on them.

What Else Does Size Do?

Not a whole heck of a lot. In 3.5e, small creatures got an AC boost, larger creatures an AC deficit, but this no longer exists in 5e.

Size does have an impact on the Encumbrance load that can be carried, but I try to avoid Encumbrance rules.

D&D 5e Rules – Size!