RNG and drop chance is one of most confusing and frustrating subjects for Warframe players. Not only because of the math but because of all the half-truths found in forums and reddit. That is why I initially created a youtube video about this topic. This blog post is a loose transcript of said video.

The video for this transcript can be found below.

RNG stands for random number generation and simply describes a tiny piece of software tossing the coin or rolling the dice for you. There is nothing fancy about this and in most programming languages it is just one line of code that decides about your luck.

This is how a success drop is calculated in Java:

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if(ThreadLocalRandom.current().nextInt(100/DROPCHANCE)==0) |

Coming from the “rolling the dice” analogy: Given that noone has manipulated the RNG software this RNG represents a perfect die that is rolled by a perfect hand on a perfect table. RNG is bound by the rules of probabilty. Here are the most important facts:

- Each time you roll the die your dop chance stays the same. If you want to roll a 6 there is a 1 in 6 chance – meaning 16.67% drop chace – each time the die is rolled.
- A 16.67% drop chance translates to 1 in 6 only in math terms. This is just for the definition and has nothing to do with how probability actually works. 1 in 6 is an average if you repeat something long enough. Long enough means hundreds or thousands of times.
- There is no pattern when the number 6 will appear when you roll the dice. If there was a pattern that could be calculated we would not have a gambling industry that makes decent money from people being unlucky. This is also known as Gamlers Fallacy.
- Repeating something decreases the probability of being unlucky. This is common sense. In math terms this is called combination and we can calculate it. But there is a limit to that calculation because probability will never allow us to make a 100% probability prediction.
- Point 3 (no pattern, Gamblers Fallacy) and point 4 (repetition for better drop chances) seem contradict each other. But both are correct.

Using combination to calculate the probability of getting the drop with repeated runs is a good indicator of how many runs you might have to expect. But let’s not forget it is just an indicator and not reliable number.

This is the formula that is used to calculate the probability of not failing after X runs:

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1 - ((1-dropChance/ 1)^numberOfRuns) |

The result of the above formula will always be followed by “chance of getting the item at least once”. Thus indicating you could have gotten the drop even earlier.

By turning the formula upside down you can also calculate how many runs it will take you to have a say 90% or 99% probability.

You can use the website dropchance.guru to do all these calculations. You will see at a glance how many runs back to back give you a 90% probability of the item drop. And 90% is a realistic indication of what to expect in terms of number of runs.

Drop chance in percent works differently than your everyday percentage calculation. Drop chance in probablity should be understood in the context of doing hundreds or even thousands of repetitions.

Although being contradicting statements, not being able to predict a drop and at the same time being able to calculate the probability of repeated runs are both correct,

I would encourage you to calculate the probability of repeatedly doing run with a certain drop chance to get a more realistic expectation.

One final advice: Very bad luck happens and it happened to every Warframe player. But we have the rare opportunity of avoiding very bad luck by the use of platinum. This is an option you should consider when the drop does not occur after you exceeded the calculated “90% chance” runs.

There are so many ways of getting platinum in Warframe that you should consider doing something different just to get platinum and the buy whatever does not drop for you with said platinum (YT: How to make platinum in Warframe).

- https://en.wikipedia.org/wiki/Law_of_large_numbers
- https://en.wikipedia.org/wiki/Gambler%27s_fallacy
- https://en.wikipedia.org/wiki/Probability_theory