Item drops

Items that drop from monsters or item boxes all follow a common set of drop rate calculations that determine which item drops, if one drops at all. Items obtained via other methods, such as gambling Meseta with Coren or redeeming Lucky Coins in Gallon's Shop, use their own unique sets of calculations. If chance is involved in obtaining items, the mechanism by which the drop is determined is commonly referred to as a roll.

Item rolls

A roll can be envisioned as rolling a many-sided die, where rolling a 1 means the item will drop. For example, if a monster drops an item with a 1/200 drop rate, it is equivalent to rolling a 200-sided die.

Monsters

Each time a monster is defeated, the game executes several rolls to determine whether an item will drop, and if so, what that item will be. Depending on the first roll, two different roll orders will be executed in sequential order:

• The game rolls based on the monster's drop anything rate (DAR) to determine if the monster has the possibility of dropping anything. If this roll is successful, the following rolls are executed:
  • The game rolls to decide if the monster will drop its specified rare item (depending on area, section ID, and difficulty)
  • The game rolls for event drops, such as Event Egg, Halloween Cookie, or Present (Christmas)
  • The game rolls for music disks (1/600 from any monster)
  • The game rolls to determine whether the drop is Meseta, a tool, or the monster's set drop. Each of these categories has an equivalent 1/3 chance of being rolled
• If the DAR roll is not successful. the following rolls are executed:
  • The game rolls for event drops, such as Event Egg, Halloween Cookie, or Present (Christmas)
  • The game rolls for music disks (1/600 from any monster)

Contrary to its description, items (event & music) can still drop with an unsuccessful DAR roll. If the event and music roll also fail, the monster will drop nothing.

Drop rate boosts

The chance to obtain items from monsters can be increased with drop rate boosts. DAR boosts increase the chance to obtain any item at all from monsters, which can also help with its designated rare drop. Rare drop rate (RDR) boosts only increase the chance for the designated rare drop. However, a monster can't have more than 100% DAR. Certain monsters already have 100% (bosses, rare monsters) or otherwise high DAR, meaning strong DAR boosts like the 25% weekly boost won't have their full effect. A similar rule applies to RDR, in which the maximum RDR can only be boosted to 7/8 (87.50%). This, however, applies to very few monsters (e.g. rare Rappies from VR Temple).

Drop rate boosts are added multiplicatively to a Monster's DAR and RDR. For example, if a monster has a 30% DAR, 1% RDR and a DAR boost of 25% and a RDR boost of 5% is active, the overall chance of the monster dropping its rare item is 30% * 1.25 * 1% * 1.05 = 0.39375%.

The drop charts show the combination of a monster's DAR and RDR. Individual DAR and RDR values are visible by hovering with a mouse over the drop rate or by tapping on them on mobile devices.

Set drops

A monster's set drop is the type of item that it will drop if it fails its rare item roll and doesn't drop either Meseta or a tool. A set drop is a category of item, not a specific one; for example, a Bartle's set drop is a weapon, so it can drop any weapon that would be able to be dropped in the area and section ID it appears in. A set drop can be a Weapon, a Frame, a Barrier, a Unit, or nothing.

Rare monsters

Some monsters can spawn as a rare variant. The spawn rate is 1/500, with the exception of the Episode 4 boss Kondrieu spawning at a rate of 1/10. Rare monsters have 100% DAR and a very high RDR. The overall chance to obtain an item from a rare monster can be calculated by combining the spawn rate with the RDR. For instance, on Episode 1 Ultimate, Hildetorrs spawn with a rate of 1/500 and drop a Heaven Punisher on Bluefull ID with a drop rate of 1/204.8. The overall chance to obtain this item from a Hildelt thus is 1/102,400. The weekly Rare Monster boost increases the spawn rate by 50%, pushing it to 1/333.33 (1/6.67 for Kondrieu).

Item box

Some item boxes may be set to drop specific items (e.g. some boxes in 1-1:Planet Ragol will only ever drop Monomates), or specific categories of items (e.g. some boxes in 1-3:Subterranean Den will only ever drop tools).

For non-drop-specific item boxes, each time an item box is opened, the game rolls to determine whether an item will drop, and if so, what that item will be in the following order:

1. The game rolls to decide if the box will drop its specified rare items (depending on area, section ID, and difficulty). In many areas, item boxes have multiple rare drops assigned to them. The roll order is from top to bottom in the drop charts
2. The game rolls to determine whether the drop is a weapon, frame, barrier, unit, tool, Meseta, or nothing (depending on area and difficulty; Yellowboze has a higher chance to obtain Meseta from item boxes).

Item box drops are not affected by any drop rate bonuses, including (but not limited to):

• drop anything rate (DAR);
• rare drop rate (RDR);
• Anguish common weapon rates;
• Photon Drop drop bonuses;
• event drop rate bonuses;
• altered weapon percentage patterns from Anguish

Calculation

The overall chance to obtain an item is best explained in an example. Assuming the Easter event is currently active, Event Eggs can be obtained by killing monsters. Claws have weapons as a set drop. The calculation of receiving a weapon box from killing a Claw on Ultimate is executed by following the roll order from above:

• DAR roll successful: 3/10 (30%)
• RDR roll fails: 1 - 1/64 = 63/64
• Roll for Event Egg fails: 1 - 1/500 = 499/500
• Roll for music disk fails: 1 - 1/600 = 599/600
• Roll for set drop successful: 1/3

The overall chance can now be calculated by multiplying the above rates:

3/10 * 63/64 * 499/500 * 599/600 * 1/3 = 1/10.89 (9.18%)

From this point, further calculations can be performed in a similar fashion to determine more specific drop rates, e.g. which weapon will drop and with what attributes (see weapon attribute drop tables for further information).

Event items and music disks

The overall chance to receive event and music disk drops is more complicated due to them appearing in both roll orders above. The calculation is not as straightforward as multiplying all probabilities in order. Once the calculations are simplified, for any given monster with a DAR% and RDR%, event items (dropping with "event rate") and music disks (1/600) drop with the following rates:

• Event item: (1 - DAR% * RDR%) * "event rate"
• Music disk: (1 - DAR% * RDR%) * (1 - "event rate") * 1/600

This shows that a monster's DAR and RDR have an effect on event and music disk rates.

Multiple rolls

The overall chance of obtaining items by killing several monsters or destroying several boxes can also be calculated. For multiple rolls, the overall chance to receive a drop naturally increases. However, this increase is not linear. The increase is determined by following the binomial distribution formula:

chance of at least 1 drop = 1 - (1 - drop rate) ^ (number of events)

Using the above example, the overall chance of receiving at least 1 weapon box from a Claw by killing it 10 times is:

chance of at least 1 drop = 1 - (1 - 1/10.89) ^ (10) = 1/1.62 (61.83%)

Average drop chance

Killing more enemies naturally increases the likelihood of receiving an item, but it will never be 100% guaranteed. This is contrary to the popular belief that killing a monster X times for its 1/X item drop will give you a guaranteed drop. In reality, the overall chance in this case always comes out to roughly 63% (approaching 1 - 1/e, where e = Euler's number). This is statistically defined as the average chance where at least 1 drop will occur, and is particularly useful when performing calculations such as "how many runs will it take to get this item?"

Combined drop rates

Some monsters drop the same item but with different drop rates. For a drop rate A and a drop rate B the combined drop rate C is:

C = A + B - A * B

For instance, if one enemy drops an item with a drop rate of 1/2 and another with a drop rate of 1/4, the overall chance of receiving at least 1 drop from killing both monsters is:

1/2 + 1/4 - 1/2 * 1/4 = 1/1.6 (62.5%)

Multiple drops

The numbers above show the process of obtaining at least 1 item, which is sufficient for most players who hunt for a certain drop once. The chance to obtain multiple items can be calculated too. For example, if a monster drops an item with a drop rate of 1/200 and is killed 100 times, the chance of it dropping 3 items or more can be calculated:

chance of at least 3 drops = 1 - P(0) - P(1) - P(2), where P(k) is the chance of exactly k item drops.

So, in this example, the chance of receiving exactly 0, 1 or 2 drops has to be calculated. The general formula for P(k) is:

P(k) = n_C_k * p^k * (1-p)^(n-k), where:

• n: number of trials, in this example 100 monster kills
• k: number of successes, which for P(0) is 0, P(1) 1, etc.
• p: probability of success, which is the drop rate of 1/200
• n_C_k: the binomial coefficient, which is defined as n!/(k!(n-k)!) with "!" referring to the factorial

The process of evaluating each P(k) value is the same, it is shown here for P(2):

• n = 100
• k = 2
• p = 1/200
• n_C_k = 100!/(2!(100-2)!) = 4950

P(2) = 4950 * (1/200)^2 * (1-1/200)^(100-2) = 1/13.21

Repeating the process for P(0) and P(1) we arrive at:

chance of at least 3 drops = 1 - 1/1.65 - 1/3.29 - 1/13.21 = 1/70.91 (1.41%)