Item Repair is a feature that allows players to repair damaged tools, armor, or other items with durability by combining them on a crafting grid. Two items of the same type and material can be placed anywhere on the crafting grid, and the result is a single repaired item. The repaired item will have usage points equal to the sum of the old items' usage points plus a 'repair bonus' of 5% (10% before 1.4) of the item's maximum uses, up to a limit of the maximum durability for that item.
Even if both items were enchanted with exactly the same enchantments, the repaired object will always be unenchanted. Hence, given the current random enchantment system, using a 'junk' item in a repair may sometimes be useful for removing an unwanted enchantment from an item prior to trying to enchant it again.
Repairing gives a slight benefit in conserving inventory space, as it combines two non-stackable objects into one, and the ~5% 'repair bonus' allows you to get slightly more total uses out of tools, which helps eke out resources a little further.
Tools made of different materials (for example, a wood and a stone pickaxe) cannot be combined.
 Formula for uses restored
The formula for determining how many uses a repaired item will have restored to it in the crafting box, is as follows:
min( Item A uses + Item B uses + floor(Max uses / 20), Max uses)
'floor' means round down to the smaller integer, which rounds the (possibly fractional) 5% bonus. 'min(x,y)' means whichever of x or y is smallest, which effectively limits repairing result to "Max uses" (repair to 100%)
Example: Two stone axes have 10 and 45 uses. A newly-crafted stone axe would have 132 uses.
- 10 + 45 + 132/20 = 55 + 6.6 = 61
Or, in terms of percentage (approximated):
- 7.5% + 34% + 5% = 46.5%
Thus, the greatest benefit is gained when the two items have a combined durability of at most approximately 95%. You can combine 47.5% + 47.5%, 94% + 1%, 10% + 10% or any other values that total 95% or less. The order in which items are combined does not matter; one sequence of repairs gives exactly the same durability as any other.
However, note in the example, repairing a stone tool restores a bonus of 6 durability, which is actually only 6/132 = 4.5%. The precise combined durability for efficient repairs is shown in the following table.
|Item||Actual bonus (%)||Actual bonus (uses)||Combined durability (%)||Combined durability (uses)|
|Carrot on a Stick||3.8%||1||96.2%||25|
|Flint and Steel||4.6%||3||95.4%||62|
A good strategy is to wear down two items until both have less than 95% combined durability remaining, but are not so damaged that you risk accidentally breaking them. Put each item in a crafting slot, and check whether the resulting repaired item still has a damage bar. If it does, you can be sure of gaining the full 5% repair bonus for combining those two items, and if it does not, you will lose some of the repair bonus. (A 'perfect' repair is theoretically possible, but unlikely in practice.)
Note that combining items whose combined durability is more than 100% actually wastes more resources than simply using tools until they break.
The precise combined durability for efficient repairs for all types of armor is shown in the following table.
|Armor piece||Actual bonus (%)||Actual bonus (uses)||Combined durability (%)||Combined durability (uses)|
 Anvil Repair
An Anvil (introduced in version 1.4.2) can also repair items in two different ways. This will cost experience levels, but unlike the crafting table, the anvil will preserve or even enhance the target's enchantments. The anvil can combine the enchantments on two similar items, or rename any item (not just the ones it can repair). The costs are complex, so only a summary is given here.
When working on items in an anvil, you pay levels based on several factors, including the enchantments it has already, any enchantments you may be adding, the amount of damage you are repairing, whether the item has previously been repaired (or renamed) in an anvil, and the type of the item (specifically, its maximum durability). If the cost would exceed 39 levels, the anvil will refuse the job, declaring it "too expensive". (This limit is lifted in creative mode.)
The first repair mode is similar to repairing in the crafting box, in that you combine two items of the same basic type, a "target" and a "sacrifice". These can be any item with durability, including such things as shears, but the items must match—you can't repair a gold chestplate with an iron one. The resulting durability will be the sum of the two item's durability, plus a bonus of 12% of the type's maximum durability. If the sacrifice is unenchanted, this will be relatively cheap for most items, costing one or two levels on top of the base value and prior-work charge. However, bows and diamond armor can cost up to 5 levels, and diamond tools up to 17. The exact cost depends on the durability of the sacrifice item, as well as the maximum durability for its type.
If the sacrifice is enchanted, some or all of its enchantments can be transferred to the target, at various additional costs. There are restrictions:
- Some groups of enchantments are incompatible—for example, you can't add Smite to a Sharpness sword. However, it does cost something if you try to!
- If the target lacks that enchantment or has a weaker version, it gains the enchantment at the sacrifice's level. You pay according to the type of enchantment and number of levels gained.
- If the target and sacrifice have it at equal levels, the target gains one level (unless they are already at the maximum level). Even if it's maxed out, you pay something for this case.
- If the target already has a higher level, it is unchanged. (No cost.)
You are charged for each enchantment transferred, and some cases where it wasn't. If you are also repairing the target, the costs combine, but some of the component costs only get charged once.
The anvil's second repair mode applies only to those tools whose material is in their default name, such as an Iron Sword or Leather Cap. Such items can be repaired by adding units of their material. However, other tools such as bows and shears can not be repaired this way. To use this mode, you put the item to be repaired in the first slot, but in the second slot you put units of the item's material -- e.g, iron ingots for iron tools/armor or pieces of leather for leather armor. A special case is the rare chainmail, which can be repaired with iron ingots. Each material unit repairs 25% the item's maximum durability, up to 100% repair, and any overflow is discarded. The cost again depends on the item's enchantments, plus a per-unit cost. Using multiple units costs more up front, but it saves in the long run, since you pay for the item's enchantments each time you put the item in the anvil. For most items, the unit cost is the number of enchantments on the item, plus 1. Diamond tools and swords are more expensive—above the number of enchantments, you pay 3 more per diamond used. However, you can get a bargain on the last or only diamond, if it didn't have much to repair.
For both modes, you also pay a penalty if the item has previously been worked on in an anvil. This penalty can be minimized by using the anvil's other function to rename the item.
 Villager Trading
Priest villagers may offer to enchant an item (chosen at random) at the cost of 2-4 emeralds. The item's durability is ignored and the resulting enchanted item will always be unused.
|1.9pre3||Added the capability to repair items.|
|1.4.2||Bonus for (traditional) item repairing is reduced to 5%. Prior this update, this bonus was 10% of the max durability.|
|1.4.2||12w41a||Added the anvil. The original item repair system is unchanged.|
A series of screenshots showing the new item repair interface.