The MVP can be calculated using computer simulations known as PVA (Population viability analysis) where populations are modelled and future population dynamics are projected

For example (and this is just an example these figures are not real) a PVA might be run on a Giant Panda population It might be found that with a starting population of 50 Pandas the population goes extinct 30 out of the 100 times once the simulation has reached 100 years It might go extinct because you start to get inbreeding depression or a natural catastrophe wipes out a large number of the Pandas there are various reasons Extinction 30 out of 100 runs means that the population survived on 70 of the runs giving a survial probability of 70% Now say you re-run the simulation but this time with a starting population of 60 Pandas This time the Panda population only goes extinct on 4 of the 100 runs The Panda population is now large enough to recover from or buffer the effects of natural catastrophes and other stochastic events so the population is able to survive more easily With a starting population of 60, the survival probability is 96 out of 100 or 96% So 60 Pandas becomes your Minimum Viable Population You could then re-run the simulation with a range of starting sizes to determine this figure more accurately (ie perhaps it is 57 or 58)

If this was a real situation and you were a conservation manager you would know that you must somehow increase the number of Pandas in your reserve to at least 60 if you want them to survive for the next 100 years This might be achieved by a captive breeding breeding program or through bringing them in from other reserves

Note that there is debate on the accuracy of PVAs