Gacha Probability Calculator#

Enter a banner’s base rate and the number of pulls you plan to make, and this tool instantly shows your real chance of landing at least one hit. It answers the question every gacha player should ask before spending: what are my actual odds?

Calculator#

How to Use This Calculator#

Enter the banner’s published per-pull rate as the base rate — for example 0.6% for a 5-star character, 0.7% for a 5-star weapon, 2% for a rare item. Put your budget in number of pulls. The results show three things:

1. Chance of at least one hit — the number you actually care about. Intuition overestimates it: at 0.6%, 90 pulls gives you only about a 42% chance of at least one hit.
2. Chance of getting nothing — the other half of the coin. It shrinks slowly: each extra pull only multiplies your failure chance by (1−p).
3. P50 / P90 / P99 benchmarks — for 90% confidence at a 0.6% rate you need roughly 383 pulls; for 99%, about 767. Most “terrible luck” stories fall inside these statistical lines.

FAQ#

Why doesn’t this match the game’s “consolidated rate of 1.6%”?

Published consolidated rates usually fold pity, off-banner and rate-up mechanics into a long-term average. This tool models independent pulls with no pity — each pull identical and independent. Different measurement, no contradiction.

What about pity systems?

Banners with hard pity guarantee a hit at a set pull count, so your real odds are higher than shown here. Treat this calculator as a lower-bound estimate for the no-pity case.

I went 300 pulls without a hit — is the rate fake?

At 0.6%, the chance of 300 consecutive misses is about 16.4% — one in six players. At 500 pulls it’s about 4.9%: rare, but entirely within normal statistics.

Can it compute pulls after losing a 50/50?

Yes — just enter your remaining budget as the pull count. This tool doesn’t model game-specific soft pity values, since those differ per game; defer to official rules.

Three Intuition Traps#

Bad gacha decisions rarely come from bad math — they come from intuition failing in three predictable ways:

Trap 1: The gambler’s fallacy. “I’ve gone 80 pulls without a hit, so the next one is due” — no. Under a no-pity model every pull is independent; after 80 misses, pull 81 still has exactly the same base rate. Streaks don’t bank luck. Hard-pity games are the exception, and that comes from the pity system, not from mysticism.

Trap 2: The hot-hand fallacy. “Feeling lucky today, two 5-stars in a row, one more session” — equally wrong. Past hits don’t change the distribution of the next pull. “Streaks” are your memory misreading random noise.

Trap 3: Survivorship bias. Your feed is full of double-rainbow 10-pull screenshots; nobody posts “600 pulls, nothing.” Silent unlucky players vastly outnumber the lucky ones — they just don’t upload. Judge your expectations by the cold numbers from this tool, not by the highlight reel.

Why Published Rates Differ by Region#

If you compare announcements across servers, the numbers don’t always match:

• Mainland China: regulators require exact rates and pity mechanics to be published — usually the most detailed disclosure
• Japan: under the Act against Unjustifiable Premiums and Misleading Representations, rate claims need a reasonable basis; off-banner (“suri-nuke”) rates are often listed separately
• Western servers: some publishers only publish a “consolidated rate” or a range, with less detail than Asian servers

This explains a common confusion: the JP announcement says 0.8% while the CN one says 0.6% — often different measurement conventions (with/without rate-up weighting, with/without pity), not favoritism. Plan your budget against your own server’s published terms.

Planning Advice#

Treat gacha as a budget problem, not a luck problem: estimate how many pulls your target realistically takes using the P90 line, then decide what to spend. Every model still runs into one hard fact — each pull is independent, and no outcome changes the next one.