Gacha banners rarely use a flat rate — they use soft pity that ramps the chance near a hard guarantee, which makes naive probability estimates wrong. This calculator models the real ramping rate so you know your true odds within a set number of pulls and exactly how many pulls guarantee the drop.
How it works
Below soft pity each pull uses the base rate. From soft pity to hard pity the per-pull rate rises linearly to 100 percent. The cumulative chance multiplies the miss probabilities of each upcoming pull:
rate(n) = base if n < softPity
rate(n) = base + (1 − base) × (n − soft) / (hard − soft) if n ≥ softPity
P(at least one) = 1 − Π over the next pulls of (1 − rate(n))
At n = hardPity the rate is 1, so a pull is guaranteed there at the latest, and
pulls-to-guarantee is simply hardPity − currentPity.
Example and tips
With a 0.6 percent base, soft pity at 74, and hard pity at 90, a player at pity 0 has only about a 65 percent chance within 80 pulls but a 100 percent guarantee by 90. If you are already at pity 74, the very next pulls carry a sharply elevated rate, so saving until just before soft pity wastes no guarantee — the ramp does the heavy lifting in the final stretch.