Anvil mechanics



This page explains the mechanics of the anvil. The anvil is primarily used to repair tools, armor, and weapons, which it can do without stripping their enchantments. It can also be used to combine the enchantments of two items, to give an item an individual name, or to crush enemies or other players that walk beneath it while it is falling. All its functions, except for damaging mobs and players, cost experience levels, and some have material costs.

The anvil has five basic functions: Renaming items can be done in the same work step as repairing or combining, provided the experience cost is not too high. In survival mode, the anvil can only apply 39 levels worth of work in a single operation. If the job would cost 40 or more levels, it is rejected as "Too Expensive!". This does not apply in creative mode.
 * Renaming any item, including normal blocks. Note that most blocks lose the rename when placed.
 * Repairing a "tiered" item with units of its material. For example, iron ingots can be used to repair iron tools and armor. Acceptable items for repair have the material to use in their default name, except for chainmail which is repaired with iron ingots, and elytra which are repaired with phantom membranes (leather).
 * Combining two items of the same kind and material that have durability, e.g. iron pickaxes, bows, shears, etc. The durabilities combine similar to using a crafting table, and the enchantments are combined following rules detailed below.
 * Combining a tool with an enchanted book to add the book's enchantment to the tool. This costs much less than combining enchantments from two similar items, and can give enchantments to items that they could not get at an enchanting table.
 * Crushing any players or mobs who happen to walk under or be under the anvil while it is falling.

Prior work penalty
Regardless of the work being done, be it rename, repair, or combine, an extra cost is imposed to work on an item that has previously been altered in an anvil—the "prior work penalty". When an item is new, this value is zero.

Each time an item is worked on an anvil (except when renaming only), the number of times the item has been worked previously is taken as n, the number 2 is raised to the power of n, and then 1 is subtracted. Thus if an item has been worked n times, the penalty is 2n-1. After six workings, the penalty is 63 levels (26-1), making any further repair or enchantment impossible in survival. After 31 workings, the penalty is 2147483647 levels (231-1) rendering further workings impossible in any mode.

Combining two items also combines the penalties for both items. The penalty on the resulting item is based on the input item with the higher penalty. For example, combining items with penalties 3 and 15 pays a penalty of 18 levels. The item with a penalty of 15 has been worked 4 times prior (24-1=15). Thus the combined item, having been worked 5 times now, now has a penalty of 31 (25-1).

This penalty applies even to items that do not take damage, like enchanted books. Thus, combining 4x Fortune I books to create a single Fortune III book results in a penalty of 3.

Item repair on a crafting grid removes all prior work penalties, and also remove any enchantments. If a grindstone is used, the item keeps its custom name, and some XP from enchantments can be reclaimed.

Renaming
Renaming always costs a single level, in addition to any prior work penalty. Renaming does not increase the prior work penalty.

If the item is being renamed only, without being repaired or enchanted, the maximum level cost is 39 levels even if the prior work penalty is higher. However, once the penalty reaches or exceeds 2147483647 further renames become impossible.

Stackable items can be renamed as a stack, while paying a single prior work penalty and a single level for the rename. Note that renamed items in general do not stack with normal items, and renamed blocks lose their name when placed.

Unit repair
Repairing a "tiered" target item using units of its material restores up to 25% total durability per unit and costs 1 level per unit of material used in addition to any applicable Prior Work penalties.
 * The material to use is in the original name of the item, except for chainmail which uses iron ingots, elytra which uses phantom membrane, and turtle shell which uses scutes.
 * Materials include leather, wood planks, cobblestone, iron ingot, gold ingot, and diamond.
 * Common tools you cannot repair in this way include bow, flint and steel, shears, fishing rod, and carrot on a stick.
 * If the stack of raw material has been renamed, its prior work penalty is paid once regardless of the number of units being used in the repair.
 * Due to the rapid increase in prior work penalty for each repair, it is generally most effective to use an item almost to the breaking point and then repair using four units of raw material at once (or by combining with a newly crafted instance of the item).

Combining items
The anvil can be used to combine two items of the same type and material, or an item with an enchanted book. This applies only to items with durability: swords, tools, and armor, as well as enchanted books. The first/left item is the target item, the second/right item is the sacrifice item, which is destroyed. Combining two similar items does either or both of two things. Each of these costs levels, but if they're both done at once, part of the cost is shared:
 * The target is repaired, adding the durability of the sacrifice plus a bonus of 12% of the maximum durability, up to the item's maximum durability. If the target item is undamaged, there is no charge for repair, otherwise the cost is 2 levels.
 * If the sacrifice has enchantments, it also tries to combine the sacrifice's enchantments onto the target. Regardless of whether any enchantments on the target are actually changed, the cost is based on the total enchantments on the target and sacrifice. For each enchantment on the sacrifice:
 * If the target has the enchantment as well...
 * and the sacrifice level is greater, the target is raised to the sacrifice's level.
 * and the sacrifice level is equal, the target gains one level, unless it is already at the maximum level for that enchantment.
 * and the sacrifice level is less, nothing changes on the target.
 * If the target does not have the enchantment, it gains all levels of that enchantment, unless it already has an incompatible enchantment. Enchantments are incompatible if both are in one of the following groups:
 * Sword: Sharpness, Smite, and Bane of Arthropods
 * Tool: Fortune and Silk Touch (as of Java version 1.12.2 you can combine these; the sacrifice item's enchantment is lost)
 * Armor: Protection, Fire Protection, and Projectile Protection
 * Boots: Depth Strider and Frost Walker
 * Bow: Infinity and Mending
 * Crossbow: Multishot and Piercing

The total cost for combining two similar items is the sum of:
 * Prior Work penalties of both target and sacrifice.
 * If renaming, the extra cost of renaming
 * If the target item is not at full durability, the repair cost of 2 levels.
 * If the sacrifice has enchantments, the enchantment cost.

If the sacrifice is a book, there is no repair, but the anvil tries to combine the book's enchantments onto the target. The item can also be renamed at the same time. The enchantment cost is generally less than for combining two similar items.

Costs for combining enchantments
(This is just the enchanting cost. The total cost outline is in Combining items.)
 * For each enchantment on the sacrifice:
 * Ignore any enchantment that cannot be applied to the target (e.g. Protection on a sword).
 * Add one level for every incompatible enchantment on the target (In Java Edition).
 * If the enchantment is compatible with the existing enchantments on the target:
 * For Java Edition, add the final level of the enchantment on the resulting item multiplied by the multiplier from the table below.
 * For Bedrock Edition, add the difference between the final level and the initial level on the target item multiplied by the multiplier from the table below.

Examples:
 * Dealing with equal enchantments:
 * In the first slot, the target is a sword with Sharpness III, Knockback II, and Looting III.
 * In the second slot, the sacrifice is a sword with Sharpness III and Looting III.
 * For the Sharpness III enchantment on the sacrifice: Since the target has an equal level, add one to the target's Sharpness level giving Sharpness IV. In Java, Add 4 (multiplier 1 times 4 levels) and in Bedrock, add 1 (multiplier 1 times the increase in levels 1) to the level cost for Sharpness IV.
 * For the Looting III enchantment on the sacrifice: Since the maximum level for Looting is III, the target remains at Looting III. In Java 12 (multiplier 4 times 3 levels) is still added to the level cost while in Bedrock, 0 is added since the level did not change.
 * Thus, the enchanting cost is 16 in Java and 1 in Bedrock. The total cost for the work includes any prior work penalties, repair costs, and rename costs.
 * If combined in the other order (the sword having three enchantments as the sacrifice), there would also be a cost of 4 (level 2 times multiplier 2) for the Knockback II enchantment for both Java and Bedrock (since the target has zero levels in Knockback), giving a total enchantment cost of 20 levels in Java and 5 levels in Bedrock.
 * Dealing with unequal enchantments:
 * In the first slot, the target is a sword with Sharpness III, Knockback II, and Looting I.
 * In the second slot, the sacrifice is a sword with Sharpness I and Looting III.
 * For the Sharpness I enchantment on the sacrifice: Since the target has a higher level, the target keeps Sharpness III. But in Java, 3 (multiplier 1 times 3 levels) is still added to the level cost. In Bedrock, since the level on the target is unchanged, the cost added is 0.
 * For the Looting III enchantment on the sacrifice: Since the target has a lower level, it is upgraded to Looting III. In Java, add 12 (multiplier 4 times 3 levels) to the level cost. In Bedrock, add 8 (multiplier 4 times the increase in levels 2)
 * Thus, the enchanting cost is 15 in Java and 8 in Bedrock. The total cost for the work includes any prior work penalties, repair costs, and rename costs.
 * If combined in the other order (the sword having three enchantments as the sacrifice), there would also be a cost of 4 (multiplier 2 times 2 levels) for adding the Knockback II enchantment, giving a total enchantment cost of 19 levels in Java. In Bedrock, the looting level would be unchanged, the sharpness cost would be 2 (multiplier 1 times the increase in levels 2) plus the Knockback cost gives a total enchantment cost of 6 levels.
 * Dealing with conflicting enchantments:
 * In the first slot, the target is a sword with Sharpness II and Looting II.
 * In the second slot, the sacrifice is a sword with Smite V and Looting II.
 * For the Smite V enchantment on the sacrifice: Since Smite is incompatible with Sharpness, add 1 level in Java, nothing for Bedrock. The target keeps Sharpness II.
 * For the Looting II enchantment on the sacrifice: Since the target has an equal level, add one to the target's Looting level giving Looting III. In Java, add 12 (multiplier 4 times 3 levels) to the level cost for Looting III. In Bedrock, add 4 (multiplier 4 times the increase in levels 1) to the level cost for Looting.
 * Thus, the enchanting cost is 13 in Java and 4 for Bedrock. The total cost for the work includes any prior work penalties, repair costs, and rename costs.
 * If combined in the other order (the Sharpness sword as the sacrifice), the cost would again be 13 in Java and 4 in Bedrock with the result having Smite V and Looting III.
 * Using books:
 * In the first slot, the target is a sword with Looting II.
 * In the second slot, the sacrifice is a book with Protection III, Sharpness I, and Looting II.
 * For the Protection III enchantment on the sacrifice: Since Protection is incompatible with swords, ignore it.
 * For the Sharpness I enchantment on the sacrifice: Since the target has no Sharpness, it gets Sharpness I. Add 1 level (multiplier 1 times 1 level) for Sharpness I.
 * For the Looting II enchantment on the sacrifice: Since the target has an equal level, add one to the target's Looting level giving Looting III. In Java, add 6 (multiplier 2 times 3 levels) to the level cost for Looting III. In Bedrock, add 2 (multiplier 2 times the increase in levels 1) to the level cost for Looting.
 * Thus, the enchanting cost is 7. The total cost for the work includes any prior work penalties and rename costs.

Trivia

 * Enchantments that are added to raw materials (e.g. an Iron Ingot with Sharpness III) are ignored when doing unit repair, not combined.
 * Because prior work penalty is charged for any rename, it is most economical to rename a weapon before repairing or enchanting it, minimizing the penalty the player must pay for the rename.