Item Stacking Calculator

Two ways an item can stack

Most items in Risk of Rain 2 add their value directly. Two Tri-Tip Daggers bleed for twice what one bleeds for, and ten stack for ten times. That is linear stacking, and it is what the overwhelming majority of the item list does — 139 of the 145 rows in the community table carry a linear curve.

A handful of items behave differently. Instead of adding to the outcome, each stack adds to a denominator, so the effective value follows 1 − 1/(1 + k×n), where k is the per-stack figure and n is the stack count. The result is a curve that climbs steeply at first and then flattens, closing half of whatever gap remains with every doubling of stacks, and never quite arriving at 100%.

Only 6 items use it: Tougher Times, Stun Grenade, Sentient Meat Hook, Tentabauble, Old Guillotine and Elusive Antlers. Four of those six roll a single chance and are the ones this page computes. The other two change a threshold or an interval rather than rolling, so they are listed but not calculated.

Worked example: Tougher Times

Tougher Times states a 15% chance to block incoming damage, and its own description adds that the effect is unaffected by luck. Plugging k = 0.15 into the curve gives a first stack worth 13.04%, and ten stacks worth 60%. Both of those figures match the numbers the community has used for the item, which is the check that the formula on this page is the right one.

The third column is the one worth reading. It is the marginal gain, and it is why a wall of Tougher Times looks unimpressive in the numbers and still performs: the point of the item is not the size of any single block but the share of hits that stop being relevant.

Every hyperbolic item

Confirmed by official sources — per-stack values are taken from each item's own description, and the curve classification from the community item table's stacking column.

Where the curve changes your build

The practical consequence is that hyperbolic items are worth picking up early and worth picking up repeatedly, but for different reasons. The first copy is the most efficient single item you can take, because it converts a 0% chance into something meaningful for one stack. The tenth is inefficient by comparison and still correct to take, because the alternative to a 60% block chance is not a 60% block chance from anywhere else.

That also explains why the same item reads as overrated and as mandatory depending on who you ask. Measured in marginal gain it is unimpressive past a handful of stacks; measured in the share of incoming damage it removes, the curve keeps paying. Both readings are of the same numbers.

The last two entries in the table are the exceptions worth knowing. Old Guillotine sets a health threshold rather than rolling, so its per-stack figure moves a cutoff for an instant kill instead of a probability. Elusive Antlers shortens an interval, which means more stacks make its orbs appear more often rather than making any single one stronger. Neither behaves like a chance item, and treating them as one is the usual mistake.

When you have a stack count in mind, the item browser is where to check what else is competing for the slot, and the tier list covers which survivors convert that mitigation into the most damage.

Watch the mechanics explained

Woolie

Explains the proc coefficient scale that the calculator on this page is built on

• Defines the proc coefficient as a value attached to every skill, and states that a coefficient of zero never triggers another item or effect.
• Makes the point that a full coefficient does not mean a guaranteed trigger — it means the item fires at its normal rate.
• Explains that halving the coefficient halves the trigger rate, which is the relationship the formula above assumes.
• Frames the topic as a trade between a faster trigger rate and a larger trigger value, and builds a calculator to compare the two.

Cap_

An introduction to proc coefficients for readers meeting the term for the first time

• Opens from the observation that the same item behaves differently on different survivors, which reads as bad luck until you know why.
• Calls the coefficient a mechanic the game never teaches, so the only way to learn it is from outside sources.
• Treats it as the deciding factor in which items are worth investing in on a given survivor.

Frequently asked

What is hyperbolic stacking in Risk of Rain 2?

It is the diminishing-returns curve used by probability items. Each stack adds the same nominal percentage to a divisor rather than to the chance itself, so the effective chance follows 1 − 1/(1 + k×n) and approaches 100% without ever reaching it. Of the 145 item rows in the community table, only 6 are marked hyperbolic — the rest add their value linearly.

Why does the tenth Tougher Times feel worse than the first?

Because it is. The first stack takes the block chance from 0% to 13.04%, while the tenth moves it from 57.45% to 60.00%. The per-stack number on the item card never changes, but the share of the remaining gap it closes keeps shrinking.

Does luck affect these chances?

Not for Tougher Times — its own description states it is unaffected by luck. That is why stacking it is the only way to move the number, and why builds that rely on it treat the item as a threshold rather than a roll.

How many stacks until a hyperbolic item is reliable?

Work backwards from the chance you need. Ten stacks of a 15% item sits at 60%; twenty sits at 75%; fifty reaches 88.24%. The curve never reaches 100%, so a hyperbolic item is always a mitigation of risk rather than a guarantee.