Your Movement Isn’t a Use-It-or-Lose-It Deal
Most players treat their movement like a turn signal: flip it once, go in one direction, done. That’s not how it works, and once you understand the real system, combat opens up considerably.
You can break your movement up across everything you do on your turn. Move 10 feet, take your action, move another 10 feet, use your bonus action, move the remaining 10 feet. The game doesn’t care about the order, only the total. That includes attacks: if you have Extra Attack, you can move between each one. Whether that’s tactically wise is another question entirely, but the option is there.
Multiple Speeds, One Bar
Here’s where it gets interesting. Some characters have more than one movement speed, whether from a racial trait, a spell like Fly, or something like Spider Climb. When you have multiple speeds, picture each one as a separate stamina bar in a video game. Every foot of movement you spend drains all of them equally, regardless of which type you’re currently using.
So if you have a 40-foot climb speed and a 30-foot swim speed, and you swim 20 feet, you’ve also spent 20 feet of your climb speed. You have 10 feet of climbing left, and zero swim. The bars deplete in lockstep.
The practical version of this: you fly 20 feet into combat, land, your target drops, and you want to walk to the next one. You still have 10 feet of walking speed available. Use it, then use your remaining fly speed if you need more distance.
Difficult Terrain and Why Climb Speed Matters
Difficult terrain costs double movement to cross. Every 1 foot of actual distance costs 2 feet off your bar. That cliff face? Ten feet of climbing without a climb speed costs you 20 feet of movement.
This is exactly why having an explicit climb speed or swim speed is valuable: it bypasses the difficult terrain penalty entirely. You move through water or up walls at your normal rate instead of burning through your movement twice as fast.
Common difficult terrain includes rubble, dense undergrowth, low furniture, and steep stairs. Yes, steep stairs. No, that’s not a joke.
Prone: The Rule Everyone Gets Slightly Wrong
Dropping prone costs you nothing. Zero movement, just fall down. Standing back up costs half your base movement speed, which for most characters is 15 feet, paid once. If you’ve already spent enough movement that you can’t cover that cost, you stay down until next turn.
At range, enemies shoot at you with disadvantage while you’re prone, which is occasionally worth the trade. In melee, they get advantage, which is not.
Sizes and Squeezing
On a grid, each 5-by-5 square represents 5 feet. Small and Medium creatures both occupy one square. Large is 10 by 10 (four squares), Huge is 15 by 15, Gargantuan is 20 by 20 or larger, and Tiny creatures share a square at 2.5 by 2.5.
You can squeeze into a space one size category smaller than you, but doing so treats the movement as difficult terrain. Moving through a friendly creature’s space is free. Moving through a hostile creature’s space requires them to be at least two size categories different from you, and it also counts as difficult terrain.
Diagonal movement on a grid costs 5 feet per square, same as cardinal movement. The Pythagorean theorem has been officially overruled in the interest of everyone’s sanity. One more corner rule worth knowing: you cannot cut diagonally around a wall corner. If the squares to your right and above you are both clear, diagonal works. If either one has a wall, you take the long way around.
For additional reference, see Player’s Handbook Chapter 9 (Combat) and the sections on movement, position, and being prone.