Drain Rate

The Drain Rate of Prayer is the rate at which with your Prayer points lowers, relatively. The unit of measurement with prayer drain is the combat round, which is in intervals of about three seconds or more precisely 3.33 seconds. Having a prayer with drain rate of 60, the player's points decreases by 1 for every round. If the drain rate is 30, then the points will decrease 1 for every two rounds. If the drain rate is 5, then the points will decrease 1 for every 12 rounds. When using multiple prayers, the drain rate gets added up into the formula and becomes a factor of the base round. For instance, if the player has activated Superhuman Strength + Improved Reflexes + Paralyze Monster, then they would get a combined drain rate of 30 + 30 + 60 or 120 which is 2*60, or a decrease of the players points by 2 for each round. In order to know how much is drained per second, simply multiply round by the duration of each round 3.33 seconds.

Prayer armour
Prayer armour decreases the rate at which prayer is drained. Notably, for every +1 in the prayer equipment status, the player can expect a reduction of about 3.1-3.2% in their drain rate. For instance if they wear the full set of the Monks robes, they would get about 34% more time with respect to wearing armour without prayer bonus.

The maximum possible prayer added bonus is +19 having equiped the full set of Monks robes with the Holy Symbol of saradomin and provides about 59% increase of time when using prayers, with respect to not using any prayer armour.