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Loot Drop Rate Calculator

Define your own weighted loot table with item names and rarity colours, then read each item's probability, the expected pulls to your first drop, and the chance of at least one in N pulls. Hit simulate to roll a live sample and watch it converge on the theory.

ItemRarityWeight

Weights are normalised to 100%. Every pull returns exactly one row, the way a loot table or a single chest slot works.

Probability per pull
0%15%30%45%60%Gold CoinsHealth Poti…Steel SwordEnchanted R…Dragon BladePercent
Drop probability for each item on the table
xPercent
Gold Coins60%
Health Poti…25%
Steel Sword10%
Enchanted R…4%
Dragon Blade1%
ItemRarityWeightProbability
Gold CoinsCommon6060.0%
Health PotionCommon2525.0%
Steel SwordUncommon1010.0%
Enchanted RingRare44.0%
Dragon BladeLegendary11.0%

The item name carries its rarity colour, and the rarity word and the number sit beside it, so the odds are clear without relying on colour.

How long to your first drop
Expected pulls to first Dragon Blade100
Chance of at least one in 100 pulls63.4%

Expected pulls is 1 divided by the drop chance. Even at the expected count, you land it by then only about 63% of the time, so plan for the unlucky runs.

Roll a live sample
014284256Gold CoinsHealth Poti…Steel SwordEnchanted R…Dragon BladeCount
Simulated drop counts from 100 pulls
xCount
Gold Coins56
Health Poti…31
Steel Sword9
Enchanted R…4
Dragon Blade0
ItemRolledSample %Theory %
Gold Coins5656.0%60.0%
Health Potion3131.0%25.0%
Steel Sword99.0%10.0%
Enchanted Ring44.0%4.0%
Dragon Blade00.0%1.0%

This is one random sample of 100 pulls, so the counts wander around the theory. Roll again to see the variance, or simulate 10,000 to watch the sample settle onto the real percentages.

Share it

Copy the table as tab-separated rows for a spreadsheet, copy a plain-text summary for Discord or Reddit, or download a labelled probability card as a PNG.

The math behind a drop rate

A weighted table gives each item a share of the total weight, so an item's probability is its weight divided by the sum of every weight. In the default dungeon chest, the weights add up to 100, which makes the Dragon Blade at weight 1 a clean 1.0% per pull.

  • Probability of an item is its weight over the total weight, or, in independent mode, its own percent chance.
  • Expected pulls to your first drop is 1 divided by that probability. A 1.0% item takes about 100 pulls on average.
  • Chance of at least one in N pulls is 1 minus the chance of missing it every time, which is 1 minus (1 minus p) raised to N. At p = 1.0% and 100 pulls that is 63.4%, not 100%.

Why the expected count is not a promise

Expected pulls is an average, not a guarantee. A drop with a 1% chance takes about 100 pulls on average, but by pull 100 you have only landed it about 63% of the time. Roughly one player in three is still hunting, and about one in a hundred is past 460 pulls. That long tail is what makes a rare drop feel brutal, and it is worth knowing before you write a character grinding the same dungeon for weeks.

The simulate button is there to make the variance real. Roll 100 pulls and the counts jump around. Roll 10,000 and the sample settles onto the theoretical percentages, which is the law of large numbers doing its work.

How to use it

  • Build the table by adding a row per drop, giving each a name, a rarity colour, and a weight. Add a Nothing row to model kills that drop nothing.
  • Pick how a pull works. Weighted single pick returns one item per pull. Independent chance rolls every row on its own, so a pull can drop several items.
  • Read the odds in the probability table, then choose a target item to see the expected pulls to your first one and the chance across N pulls.
  • Simulate to roll a live sample, then copy the table or summary, or download the card as a PNG.

WriteIDE does this for your whole book, automatically

This tool handles one at a time. WriteIDE is the desktop studio that tracks LitRPG stats, items, skills, and quests across a whole novel, and keeps them correct at every scene.

Runs in your browser. Nothing you type is sent anywhere, and it keeps working with your network off.
Made with writeide.com
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