Combat level

A player's, monster's, or NPC's combat level is a number calculated using their stats to show roughly how difficult they are to defeat. All players start out at combat level 3, with the maximum combat level for players being 138, although NPCs can have considerably higher levels.

Combat level is calculated by taking into account the following skills:
 * Attack and Strength or Ranged or Magic
 * Defence
 * Constitution
 * Prayer
 * Summoning (not applied toward combat level in free worlds)

The formula for determining a player's combat level is:



Summoning and Prayer are both rounded down after being multiplied by 1/2. The final quotient is never rounded up. For example, after using the formula, a player's level is 87.975. His combat level will appear as 87.

This will give a maximum combat level of 138 for any player with level 99 Attack + Strength/Magic/Ranged, 99 Defence, 99 Constitution and 96/99 Summoning and Prayer. Free worlds do not take a player's Summoning level into account. Therefore, the maximum level for free players is 126, even if a player has trained Summoning to level 5.

Although most monsters have their levels calculated using the same formula that players use, a select few have levels manually set by Jagex that do not reflect their true stats.

Levels that are significantly lower than the player display shades of green , levels that are slightly lower than one's display yellow-green , levels that are equal to one's are displayed as yellow , and levels that are higher than yours display shades of orange  to red . In the Wilderness, levels outside the combat range will appear white. The difference in colours can be seen up to 10 levels higher or lower than your current combat level after which it will either show the brightest shade of green or red depending on whether the combat level is lower or higher.

In the Wilderness, a player's combat level is shown slightly differently. Unless a player has a summoning pouch in their inventory or a summoning familiar summoned, the combat levels gained from summoning will not be part of the players main combat level, instead, the levels they would have gained from summoning are shown as +X after their main combat level. For example, a player with no summoning pouch or familiar would be level 79+6 instead of 85.

Effects of combat level
Normally, aggressive NPC's will stop attacking a player if the player has double the NPC's combat level +1. There are exceptions, however - for example, any monsters in the wilderness that are normally not aggressive will be aggressive to players no matter what their combat level is. Also, monsters that are normally aggressive will always attack a player if they are level 69 or higher, since the maximum combat level is 138.

Monsters with a higher combat level than a player usually cannot be attacked by using a left mouse click. Instead, players need to right click and select the attack option. So, to be able to attack a Blue dragon with a simple left click, a player needs a combat level of at least 74. Many bosses and other high-leveled monsters are exceptions to this, such as the God Wars Dungeon generals, as well as popular high level monsters such as tormented demons, dark beasts, and metal dragons. All monsters in Daemonheim are also exceptions.

Players may view another players combat level by right clicking them if they have their weapons unsheathed. If their weapons are sheathed, their Skill total is shown instead. A player can toggle between showing their combat level or skill total to other players by right-clicking the [-] button on the top-right of their keybind bar and selecting Toggle-sheathe.

There are some requirements in game that require a certain combat level. There are three quests requiring a certain combat level, Smoking Kills, Dream Mentor and World Wakes. Training with certain Slayer Masters, and also the Void Knight activities Pest Control and Conquest, also have combat level requirements.

History
Before the Evolution of Combat, a player's combat level was calculated slightly differently to the current approach:

This formula meant that a player with 99 Attack and Strength would have a higher combat level than another with 99 Ranged or Magic, allowing warriors of far higher level than those of rangers and mages.

The release of Evolution of Combat changed the formula significantly, giving players a minimum level of 4 and a maximum level of 200. Constitution and Prayer were no longer taken into account, and only the highest of Attack, Strength, Ranged, Magic or Summoning, together with Defense, was used in the calculation.

The current formula was released at the same time as Legacy mode after a Power to the Players poll. It is a slightly tweaked version of the original 138 formula, changed to make Ranged and Magic equal to Melee.

Trivia

 * In DeviousMUD the highest an account ever reached was 52.
 * Past maximum combat levels include level 123 in RuneScape Classic, 126 before Summoning was added, and 200 after the release of the Evolution of Combat.
 * In Runescape Classic, players started at 1 combat. This was later changed to 3.

Combat level