In Old School RuneScape (OSRS), optimal prayer usage is crucial for success in combat, particularly against high-level bosses. Determining the most effective prayer against a given opponent’s attack style can be complex due to the numerous prayers and attack styles in the game. Tools exist that simplify this process by allowing players to input the monster’s attack style and receiving the ideal protective prayer in return. These tools function much like a calculator, hence the term. For example, if a monster uses a magic attack, the tool would recommend using Protect from Magic.
Utilizing such tools offers significant advantages. They eliminate the need for memorizing complex prayer combinations and ensure players always use the most effective defense, maximizing their survivability and reducing the risk of costly deaths. Historically, players relied on external resources like fan-made wikis or guides. The development of these calculation tools streamlined the process, contributing to more efficient gameplay and a lower barrier to entry for newer players.