How are expected attempts calculated?

Expected attempts follow the geometric distribution: one divided by the per-attempt success chance. A 65 percent chance averages about 1.5 attempts, while a 10 percent chance averages 10 attempts to first success.

What does the confidence row mean?

It shows how many attempts you need to be 50, 90, and 99 percent likely to have succeeded at least once. These come from the formula attempts = ln(1 − confidence) / ln(1 − success chance).

How does the attempt budget work?

Enter a number of attempts you are willing to make and the tool returns the probability that at least one of them succeeds, plus the total rune cost of using the whole budget. This helps you set a stop-loss before grinding.

What if the item is destroyed on failure?

Tick the consumed-on-attempt box and treat the cost per attempt as the full replacement cost of the item. The expected attempts stay the same, but the expected cost reflects that you pay for every attempt whether it succeeds or fails.

Why is there no guaranteed success?

Without a pity or guarantee mechanic, each attempt is independent, so there is always a small chance of a long losing streak. The confidence row exists precisely to show how many attempts make a success near-certain.

Elden Ring Enchant & Gear Score Calculator

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Elden Ring upgrades and enchants can swallow runes fast when the success chance is low. This calculator turns a success percentage and a per-attempt cost into the numbers that actually matter: expected attempts, expected total rune cost, and your odds within a fixed budget.

How it works

Each attempt is independent, so the math is the geometric distribution:

expected attempts   = 1 / successChance
expected rune cost  = expected attempts × cost per attempt
chance within N      = 1 − (1 − successChance)^N
attempts for C%      = ln(1 − C) / ln(1 − successChance)

If the item is consumed on every attempt, the cost per attempt is the full replacement cost, so the expected total cost climbs steeply as the success chance falls.

Example and tips

At a 65 percent success chance costing 4,000 runes per attempt, expect about 1.5 attempts and roughly 6,000 runes on average to succeed. Set an attempt budget you are comfortable with — the confidence row shows that even a low success chance becomes near-certain after enough attempts, but the rune cost of getting there can be the real limiter.