Every character and monster has a speed, which is the distance in feet that the character or monster can walk in 1 round. This number assumes short bursts of energetic movement in the midst of a life-threatening situation.
Difficult Terrain
The travel speeds given in the Travel Pace table assume relatively simple terrain: roads, open plains, or clear dungeon corridors. But adventurers often face dense forests, deep swamps, rubble-filled ruins, steep mountains, and ice-covered ground — all considered difficult terrain.
You move at half speed in difficult terrain — moving 1 foot in difficult terrain costs 2 feet of speed — so you can cover only half the normal distance in a minute, an hour, or a day.
Special Types of Movement
Movement through dangerous dungeons or wilderness areas often involves more than simply walking. Adventurers might have to climb, crawl, swim, or jump to get where they need to go.
Climbing, Swimming, and Crawling
Each foot of movement costs 1 extra foot (2 extra feet in difficult terrain) when you’re climbing, swimming, or crawling. You ignore this extra cost if you have a climbing speed and use it to climb, or a swimming speed and use it to swim. At the DM’s option, climbing a slippery vertical surface or one with few handholds requires a successful Strength (Athletics) check. Similarly, gaining any distance in rough water might require a successful Strength (Athletics) check.