🎰 Gacha Probability Calculator
Enter the drop rate and how many pulls you have to see your real chance of getting at least one, and the pulls needed for better odds.
Chance of at least one
41.82%
1 − (1 − rate)^pulls
How the gacha probability calculator works
A single pull's drop rate is misleadingly small, but over many pulls the odds of getting at least one add up. The chance of at least one success in n independent pulls is 1 − (1 − p)^n, where p is the per-pull rate. This calculator applies that formula and also inverts it to tell you how many pulls you need for 50%, 90% and 99% confidence. It computes instantly in your browser, so you can plan your spending with real numbers instead of hope.
This assumes each pull is independent at a flat rate. Many gacha games add a pity system (a guaranteed drop after a set number of pulls) and rate-ups, which this simple model does not include, so your real odds on those games are usually better than the flat estimate once pity is near. Still, the base formula is the honest starting point.
Frequently asked questions
How do I calculate gacha pull probability?
The chance of at least one success in n pulls is 1 − (1 − p)^n, where p is the drop rate as a decimal. For a 0.6% rate over 90 pulls, that is 1 − (1 − 0.006)^90 ≈ 42%. This tool does it for you.
Why is my chance lower than I expect?
Because low per-pull rates compound slowly. Even 90 pulls at 0.6% leaves a large chance of nothing, which is exactly why pity systems exist. The maths is unintuitive: getting to 90% confidence often takes far more pulls than people guess.
How many pulls do I need to be almost guaranteed?
The tool shows the pulls needed for 50%, 90% and 99% confidence at your rate. Note that reaching 99% takes many more pulls than 50%, each extra nine of certainty costs roughly the same number of pulls again.
Does this account for pity systems?
No. This uses a flat, independent rate. Games with pity (a guaranteed drop after N pulls) or rate-ups give better real odds near the pity threshold, so treat this as the no-pity baseline.
Is anything uploaded?
No. The probability is computed in your browser.