Drop chance calculator

This basic calculator shows the theoretical probabilty of succeeding by repeating something with a fixed drop chance.


chance for each run

123 runs

to have a 90% chance to get the item at least once

423 runs

to have a 99% chance to get the item at least once
Succeeding at least once
67.02% for 10 runs
89.12% for 20 runs
89.12% for 30 runs

Calculate 7.52%
Harrow Systems BP drop chance from Memphis / Phobos
Calculate 4.17%
Fleeting Expertise drop chance from Orokin Vault
Calculate 1.36%
Shotgun riven drop chance from sortie
Calculate 2.01%
Imperator Vandal Receiver drop chance from Fomorian Sabotage
Calculate 1.29%
Nitain Extract drop chance from rotation C Cache Plato / Lua
Calculate 10.53%
Hunter Munitions drop chance from Hemocyte enemy

Drop chance and RNG in Warframe video

A while back I made a video on how to use this website and on how to interpret the results. This video also covers the different aspects of probability without diving too deep into the math rabbit hole.

There is also a complete video transcript available.

The concept behind the calculated properbility
The drop chance for each individual run stays the same. Repetition does not increase the drop chance as such. What it does increase is the probability to get what you want the more repetitons you do.
But there is no guarantee for success even at 99.99% probability.
This calculator gives you an indication of the number of tries you have to expect.
The math behind number of runs
The calculation of how many tries should give at least one positive result is done by using the chance to fail.
10% drop chance means a 90% probability (0.9) to fail. For 10 runs this means a probabilty 0.910 to fail. This results in 0.35, meaning 35% chance of not succeeding in 10 runs. And this again means 65% chance of succeeding (at least once) in 10 runs.
You want to dig deeper into drop chances?

If you want to nerd out on the subject here are some additional resources:

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