Run/Walk refers to the movement speed at which a character can run or walk, measured in yards per second, in Diablo II and Diablo III. In the first game, character movement speed is constant and same for the player and most creatures.
Default walking speed is 4 y/s, running increases your speed by 2 y/s. The Paladin skill, Charge defaults to 9 y/s, but is not influenced by items that change Run/Walk speed. Running drains character's Stamina, making it impossible to run if depleted.
The limit on reduced speed for Run/Walk is 1 y/s, running speed is calculated by your theoretical walking speed, so it can fall below 3 y/s, but is also prevented from falling under 1 y/s. Note however, there is no lower limit on Charge, meaning you can charge in reverse if you are slowed below 0 y/s.
Items that provide a faster Run/Walk bonus come with diminishing returns, meaning that the higher it gets, the less of an increase you are gaining.
Skills modify your base speed (4 y/s) and provide their full listed effects without diminishing returns. Skills will also affect Charge speed.
- Light armor has no negative influence on your speed.
- Medium armor will decrease your Run/Walk by -0.2 y/s and Charge by -0.45 y/s.
- Heavy armor will decrease your Run/Walk by -0.4 y/s and Charge by -0.9 y/s.
In Diablo III, movement speed is measured in percent, with 100% (initial normal speed) being roughly 6 yards per second (much like average real-life running speed), for both heroes and most monsters. Characters no longer have Stamina, cannot walk (always run), and movement speed penalties for gear are gone. Movement speed may not be brought below 20% by negative effects (remember that monsters build up CC resistance to it while slowed down).
One may gain a permanent speed increase from items, skills and from Paragon levels. Paragon points award 0.5% speed each (up to 25% total), and Boots may roll up to +12% speed. Some Legendary and Set Items may roll movement speed as well, but normally only boots do so.
The permanent speed bonus is limited to +25%, which allows putting 50 Paragon points into the Core section and therefore freeing item affixes for more valuable stats.