Units of Measurement (from the Core Rules)

Time

The simplest units of time measurement for time in the game are the same ones we use in real life: Seconds, Minutes, Hours, Days.

In combat situations, and in some out-of-combat spellcasting situations, we change from Seconds, Minutes, Hours and Days to segments, rounds and turns, or “game time.”

At the DM’s discretion, a spell or effect with a game time limit may be stretched out when out of combat, if the effect is not affecting game play. For example, a mage could extend a faerie fire or cantrip spell without requiring an additional casting while riding on a wagon or taking a gentle walk through a forest, simply gathering the energies around himself to extend the spell. Such effects are considered “out of game time” or non-combat timed, and if they have no discernable effect on play, should be allowed.

The table below shows the in-combat or game time units and their real-world equivalent:

Unit	In Rounds	Real-World Equivalent
Hour	60	Hour
Turn	10	10 minutes
Round	1	1 minute
Segment	1/10*	6 seconds, generally
*Initiative and most spellcasting is measured in segments. An initiative of 2 goes on the second segment of a round in combat.

It is possible for a segment to “count” as more or less than 6 seconds. For example, some items of speed or weapons force an attack at the beginning or end of a round. These “outside of initiative” times are considered part of a round, even though ten segments equals one round.

Distance

For the most part, distance is measured in real-world units, standard or metric as the campaign allows. Yards are generally the standard measurement for spells and ranges, although tens of yards (1989 Player’s Handbook) and fives of yards (Combat and Tactics) are occasionally used. These are based on board hexes used for miniatures, which come in three sizes themselves. “Board Inches” are a 1^st edition AD&D measurement which usually equals 10 yards and corresponds to one grid on a miniatures sheet. This grid can be further divided into either 10ths, halves (fives of yards) or thirds, which gives the 10ft hex used in most dungeon hallways.

This can be further simplified by the DM as each medium creature taking up about a 1/3 of a 10ft hex, each small creature taking up 1/6 of a hex and each tiny creature taking up 1/12 of a hex, although the DM should use the most logical arrangement in such situations.

Volume

 Volume is primarily used for spellcasting, and in other situations should use real world measurements. In fact, the volumetric fireball of AD&D is often used as an example of a lazy measurement in gaming. In generally, volume-based spells come in two types, regular hexahedrons (cubes, cuboids, boxes, walls) or spheres, although cones, cylinders and rays are not uncommon. Regular hexahedron spells are either given in volume (cubic feet) or in surface area (square feet) but occasionally are given in “cubes.” Spells given a volume of a number of 10ft cubes can often be arranged in any form, but only in 10ft cubes (and these shapes can be represented by d6s.) Any shape where a full face of each cube touches another face of a cube may be allowed without a spellcraft roll to modify, but a successful spellcraft roll can be used to place the cubes edge to edge. Such spells cannot form cubes that are not touching at least one other cube unless it is explicitly stated as such in the spell description.

Sphere effects are generally given with a diameter (the maximum distance of a straight line from one side of the sphere to another) or a radius (the distance from the wall of a sphere to its center.) Other spells may require more complex geometry, and the DM is encouraged to use units comprehensible to his/her players