Also known as the 50th percentile, P50 is the “Best Estimate” for a quantity.  If probabilistic methods are used, there will be an equal probability that the actual value of the quantity will exceed the P50 value as fall below it. With respect to resources categorization, this is the best estimate of the quantity of hydrocarbon that will actually be recovered from the accumulation by a project. If probabilistic methods are used, there will be an equal probability that the quantities actually recovered will exceed the P50 value as fall below it.