Barrows Drop Simulator

How Barrows loot works

Opening the chest under the Barrows mounds awards 1 + brothers killed independent rolls (up to 7). Each roll first checks for Barrows equipment using 1 / (450 − 58N), where N is brothers slain. Only gear belonging to brothers you killed can appear, and the same exact piece cannot drop twice in one chest.

If the unique roll fails, the chest awards from the reward-potential table instead — coins, mind / chaos / death / blood runes, bolt racks, key halves, or (at full potential) a dragon med helm. This simulator assumes maximum reward potential (1012) so every non-unique roll can hit the full rune and bolt-rack ranges. Toggle Morytania hard diary for the +50% rune quantity bonus.

Why simulate Barrows chests?

Collection-log and ironman players often ask how many chests a full set “should” take. Expected chests for any complete set is roughly 313; a specific set is closer to 728; all six sets averages around 1,319. Running a few thousand chests here shows the variance — spooned double uniques versus long dry streaks — better than a single expected-value number.

Tips for real runs

• Kill all six brothers when hunting any unique; skipping brothers removes their entire set from the pool.
• Push reward potential into the blood-rune band if you want rune profit without overshooting into bolt racks every roll.
• Repair costs add up — pair this tool with the Barrows repair calculator.

FAQ

What is the chance of a Barrows unique with all 6 brothers?

With all six brothers killed, each chest roll has a 1/102 chance of a Barrows piece. You get 7 rolls, so the chance of at least one unique is about 1/15, and the expected pieces per chest is about 7/102.

Can I get the same piece twice in one chest?

No. Within a single chest, once a specific item is rolled it is removed from the pool for later rolls. You can still get multiple pieces from the same brother.

Does reward potential change unique odds?

No. Unique chance only depends on how many brothers you killed. Reward potential only affects the coins, runes, bolt racks, key halves, and dragon med helm table.