How does the weighted random selection work?

Each item has a numeric weight. The generator sums all weights to get W, then picks a random number u in [0, W). It walks the item list, subtracting each weight from u, and awards the item where u first reaches zero or below. An item with weight 40 in a table summing to 100 will be selected 40% of the time — regardless of how many other items exist.

What is the difference between Weight and Drop%?

Weight controls which item is selected from the table on each roll. Drop% is a second independent check — once the item is selected, the generator rolls d100 and only awards the item if the result is less than or equal to the drop threshold. You can therefore model "rare items that sometimes miss even when targeted" by giving them a high weight but a low drop%.'

What dice notation can I use in the Qty field?

The Qty field accepts a plain integer (e.g. 5), standard dice notation (e.g. 2d6), and notation with a flat bonus or penalty (e.g. 3d4+2 or 1d8-1). The minimum awarded quantity is always 1. The expected value shown in the Drop Chances tab is N*(M+1)/2 + K for NdM+K.

How is effective drop chance calculated?

Effective% = (item weight / total weight) x (drop% / 100) x 100. For example, an item with weight 5 in a 100-weight table and a 40% drop chance has an effective probability of 5% x 40% = 2% per roll. The Drop Chances tab shows this for every item so you can see at a glance how skewed your table is toward common items.

Can I save my custom loot table?

All edits are held in the page state. The tool is 100% client-side and does not upload or store any data, so refreshing the page will reset to the default table. If you want to preserve a custom table between sessions, copy the resulting roll output or note the weights manually.

How many rolls can I run at once?

Up to 100 rolls per batch and 20 batches simultaneously (2,000 individual rolls in one click). Results are appended to the history so you can compare multiple batches. The history is capped at the 50 most recent batches to keep the page responsive.

Loot Roll Generator — Gera Tools

Every dungeon master, game designer, and tabletop RPG player eventually faces the same problem: you need a believable, balanced loot table that dishes out gold and health potions freely while making that Legendary sword feel genuinely rare — without stopping mid-session to do arithmetic. This generator handles the maths and the dice so you can focus on the story.

How the maths work

The generator uses a two-stage probability model that mirrors how most physical loot tables are designed.

Stage 1 — Weighted selection. Every item in the table has a numeric weight. The engine sums all weights to get a total W, draws a uniform random value in (0, W), then walks down the item list subtracting weights until it reaches zero. The probability of selecting item i is simply:

P(select i) = w_i / W

An item with weight 40 in a 100-weight table is selected 40 % of the time.

Stage 2 — Drop check. Once an item is selected, a virtual d100 is rolled. The item is only awarded if the roll lands at or below the item’s drop-chance threshold. This lets you model “possible but not guaranteed” rewards — for example, a Dragon Scale might appear on the selection step fairly often but still miss 80 % of the time because its drop chance is set to 20 %.

Combined (effective) probability per roll is therefore:

P(awarded) = (w_i / W) x (drop% / 100)

This is what the Drop Chances tab shows, sorted from highest to lowest so table imbalances are immediately visible.

Quantity dice use standard NdM+K notation. Rolling 2d6+1 draws two independent six-sided dice, sums them, and adds 1. The expected value is N x (M+1)/2 + K, so 2d6+1 averages 8.

Preset tables explained

Three curated presets ship with the generator:

Preset	Flavour	Rarity distribution
Dungeon Chest	Classic adventurer loot	Common through Artifact
Goblin Pockets	Low-level, mostly junk	Mostly Common, one Rare
Dragon Hoard	High-value late-game	Starts at Uncommon, peaks at Artifact

The Default table is a general-purpose mix good for mid-level encounters.

Example roll

Suppose you roll once on the Dungeon Chest preset. The generator draws a random value against the total weight (100). Let us say it lands on Spell Scroll (weight 20, drop chance 65 %). It then rolls d100 and gets 42 — which is ≤ 65, so the item is awarded. Quantity is 1 (fixed), so the player receives one Spell Scroll. The effective probability of this exact outcome on any single roll is (20/100) x 0.65 = 13 %.

If the same roll had produced a Divine Artifact (weight 1, drop chance 2 %), the effective chance would have been (1/100) x 0.02 = 0.02 % — one in 5,000 rolls. That is the kind of scarcity that makes legendary items feel earned.

Building a balanced table

A healthy loot table usually follows a rough pyramid: many common items with full or near- full drop chances filling 60–70 % of effective probability, a band of uncommon/rare items in the 5–20 % range, and one or two very-rare or legendary items below 5 %. The Drop Chances tab makes this visible at a glance. If your “Legendary Sword” shows up at 8 % effective, it will feel fairly routine after ten fights — time to lower the weight or the drop chance.