BASE RNG LAB

TOOL / ROLL PROBABILITY

Build a Base RNG roll chance calculator

Use the odds currently displayed in your game. Get cumulative chance, no-hit risk, expected successes and target roll counts without a fake item database.

ROLL PROBABILITY // LIVE

Roll chance calculator

Formula verified
Chance of at least one48.7%51.3% chance of no success after 1,000 rolls
50% chance1,04035 min
90% chance3,4531.9 hr
95% chance4,4932.5 hr
99% chance6,9063.8 hr

Enter the odds shown in your game. Luck boosts may change that displayed number; this tool does not guess a hidden Luck formula.

READ THE RESULT

Expected does not mean guaranteed.

A 1-in-1,500 object has an expected wait of 1,500 rolls, but 1,500 attempts only produce about a 63.2% cumulative chance. The 90% target is much higher because unlucky streaks are a normal part of random trials.

FORMULA

Probability in one line.

chance = 1 − (1 − 1 / odds) ^ rolls

The “no success” value is the complement. Expected successes are simply rolls divided by the odds denominator.

FAQ

Calculator questions

Why did I miss after the expected number of rolls?

Expected rolls are a long-run average, not a guarantee. At 1-in-N odds, rolling N times gives roughly a 63.2% chance of at least one success—not 100%.

Does this calculator include Build a Base RNG Luck boosts?

Use the final odds shown in your game after boosts. The calculator does not invent a hidden Luck formula.

What formula does the calculator use?

For independent rolls with success probability p and roll count r, the chance of at least one success is 1 − (1 − p)^r.