OneTaskBy Tim King · Updated
Loot Drop Calculator
Rare Drop Odds After N Kills, Chests or Pulls, Tries for 50%
OneTask is free, with no sign-up, and built by one person.
If this tool saved you time, a coffee helps keep new ones coming.
How the Loot Drop Calculator works
Enter a drop rate, the number of kills, chests or pulls you plan, and how many copies you need. The loot drop calculator shows your real chance of getting them, the chance of getting nothing, the drops you can expect on average and how many tries give a 50%, 90% or 99% chance.
A 1% drop does not mean you get it in 100 kills. It means each kill has a 1-in-100 chance, and every kill starts fresh. After 100 kills about 63% of players have the item and 37% are still empty-handed. Knowing that number stops a dry streak feeling like the game is cheating.
How the loot drop calculator works
Each try is treated as independent with the same chance p. The formula for getting nothing in n tries is (1 − p)ⁿ, so the chance of at least one drop is 1 − (1 − p)ⁿ. When you need more than one copy, the calculator adds up the binomial chances of getting 0 to k − 1 drops and subtracts that from 100%.
The tries needed for a 50%, 90% or 99% chance are found by searching for the smallest n that reaches each target. For a single drop they come out close to 0.69, 2.3 and 4.6 times the "1 in X" figure.
Worked examples
Example 1: a boss has a 1% drop and you plan 100 kills. The chance of none is 0.99¹⁰⁰ = 36.6%, so the chance of at least one is 63.4%. You would need 69 kills for a coin-flip chance, 230 for 90% and 459 for 99%.
Example 2: you need three copies of a 5% drop and have 50 chests. Expected drops are 2.5, but the chance of reaching three is only 45.95%, and 7.69% of players get none at all. A 90% chance of three copies takes 105 chests.
How many tries for a 1-in-X drop
Tries needed for a 50%, 90% or 99% chance of at least one drop
| Drop rate | 50% chance | 90% chance | 99% chance |
|---|---|---|---|
| 1 in 2 (50%) | 1 | 4 | 7 |
| 1 in 3 (33.3333%) | 2 | 6 | 12 |
| 1 in 4 (25%) | 3 | 9 | 17 |
| 1 in 5 (20%) | 4 | 11 | 21 |
| 1 in 8 (12.5%) | 6 | 18 | 35 |
| 1 in 10 (10%) | 7 | 22 | 44 |
| 1 in 15 (6.66667%) | 11 | 34 | 67 |
| 1 in 20 (5%) | 14 | 45 | 90 |
| 1 in 25 (4%) | 17 | 57 | 113 |
| 1 in 32 (3.125%) | 22 | 73 | 146 |
| 1 in 50 (2%) | 35 | 114 | 228 |
| 1 in 64 (1.5625%) | 45 | 147 | 293 |
| 1 in 75 (1.33333%) | 52 | 172 | 344 |
| 1 in 100 (1%) | 69 | 230 | 459 |
| 1 in 128 (0.78125%) | 89 | 294 | 588 |
| 1 in 150 (0.666667%) | 104 | 345 | 689 |
| 1 in 200 (0.5%) | 139 | 460 | 919 |
| 1 in 250 (0.4%) | 173 | 575 | 1,149 |
| 1 in 256 (0.390625%) | 178 | 589 | 1,177 |
| 1 in 300 (0.333333%) | 208 | 690 | 1,380 |
| 1 in 400 (0.25%) | 277 | 920 | 1,840 |
| 1 in 500 (0.2%) | 347 | 1,151 | 2,301 |
| 1 in 512 (0.195312%) | 355 | 1,178 | 2,356 |
| 1 in 1,000 (0.1%) | 693 | 2,302 | 4,603 |
| 1 in 2,000 (0.05%) | 1,386 | 4,605 | 9,209 |
| 1 in 5,000 (0.02%) | 3,466 | 11,512 | 23,024 |
The 99% column is the sobering one. One player in a hundred still has nothing after more than four and a half times the listed rate. Those players exist in every large game.
Where it applies
- MMO and ARPG boss drops: most use a flat roll per kill. Old School RuneScape pets, World of Warcraft mounts and Diablo uniques are classic examples.
- Chests and containers: a fixed chance per chest opened.
- Gacha pulls: works for the base rate, but ignore it once a pity counter or soft pity kicks in, because the chance is no longer the same every pull.
- Shiny hunting and crafting procs: any fixed per-attempt chance.
Needing more than one copy
Collecting several copies is much slower than the first. At a 1% rate, 100 tries give a 63% chance of one drop but only 26% for two and 8% for three. Expected drops scale in a straight line, yet the chance of reaching a set count climbs slowly, so plan farming sessions around the 90% figure rather than the average.
Tips and pitfalls
Check the drop rate is per kill. Some wikis list a rate per item roll when a boss rolls several times per kill. If a boss rolls three times, three tries happen each kill.
Bad-luck protection changes everything. Games that raise the chance after each failure, or guarantee the item at a cap, are not independent trials. This calculator gives the worst case without protection.
Past failures do not count. If you have done 300 kills at 1%, your chance in the next 100 is still 63%. The "due a drop" feeling is the gambler's fallacy.
Group loot splits the drop. If the item drops for the group and is rolled among five players, your personal chance per kill is the drop rate divided by five.
How to read the result
The first line is your chance of ending with at least the number of drops you asked for. Chance of none is the dry-streak risk. Expected drops is the long-run average, useful for farming materials. The table shows your chance at multiples of the 1-in-X figure, so you can see how quickly the odds climb and then level off.
FAQ
If a drop is 1 in 100, will I get it in 100 kills?
Only 63.4% of the time. The chance of missing on every one of 100 independent kills is 0.99¹⁰⁰, about 36.6%. You need about 230 kills for a 90% chance and 459 for a 99% chance.
How do I calculate drop chance over multiple tries?
Subtract the drop rate from 1, raise it to the power of the number of tries, and subtract the result from 1. For a 5% drop over 20 tries that is 1 − 0.95²⁰, about 64%.
Does a long dry streak make the next drop more likely?
No, unless the game has bad-luck protection. Each roll is independent, so the chance on the next kill is the same as on the first. A long streak is simply bad luck that has already happened.
What does expected drops mean?
It is the average number of drops across many players doing the same number of tries: the drop rate times the tries. It is useful for farming materials, but any one player can land well above or below it.
See also: all Gaming & PC tools, Everyday Maths, Loans & Savings, Dates & Time, Health, Home & DIY, Unit Converters, Education, Science, Creative, Garden & Farm, Work & Business, Fun, Maps & GPS, DIY & Building, Cost Estimators, Sport & Clubs.
Related tools
Dice Roller
Roll D6, D20 or any custom die with a fair random generator.
Minecraft XP Calculator
XP needed between any two Minecraft levels, with bottle counts.
EDPI Calculator
eDPI from DPI and sensitivity, with the same feel converted to every game.
Coin Flip
A fair heads-or-tails coin flip, single or in bulk with statistics.
Pokémon Damage Calculator
Damage range, one-hit KO chance and hits to KO for any move.