Gacha banners are not flat-rate: most use a pity system where your odds stay low, then ramp sharply near a guaranteed cap. This calculator models that exact behaviour so you can see, from your current pity count, how likely your next batch of pulls is to land a top-tier item and how many pulls remain until the guarantee.
How it works
The model uses three banner parameters: a base rate p0, a soft-pity start S,
and a hard-pity cap H. The per-pull rate at pull number n is:
n < S → rate = p0
S ≤ n < H → rate = p0 + (1 - p0) × (n - S + 1) / (H - S)
n ≥ H → rate = 1 (guaranteed)
To find your chance over a range of pulls, the tool multiplies the miss probability of every pull from your current pity onward, then subtracts from one:
P(at least one) = 1 - Π (1 - rate(pity + k)) for k = 1..pulls
Example and notes
With a 0.6% base rate, soft pity at 74, and hard pity at 90, a player at pity 40 making 10 pulls is still below soft pity, so each pull is just 0.6% — a cumulative chance of about 5.8%. Push that same player to pity 70 and the next 10 pulls cross deep into the soft-pity ramp, lifting the cumulative chance well above 80%. The guarantee always lands at hard pity, so the pulls-until-guaranteed figure is simply the hard-pity number minus your current count. Match the three banner fields to your specific game for accurate odds.