Highest monthly inflation: 13,600,000,000,000,000%
Prices doubled every: 15.6 hours
The worst case of hyperinflation ever recorded occurred in Hungary in the first half of 1946. By the midpoint of the year, Hungary's highest denomination bill was the 100,000,000,000,000,000,000 (One Hundred Quintillion) pengo, compared to 1944s highest denomination, 1,000 pengo. At the height of Hungary's inflation, the CATO study estimates that the daily inflation rate stood at 195 percent, with prices doubling approximately every 15.6 hours, coming out to a monthly inflation rate of 13.6 quadrillion percent.
The situation was so dire that the government adopted a special currency that was created explicitly for tax and postal payments and was adjusted each day via radio. The pengo was eventually replaced later that year in a currency revaluation, but it is estimated that when the currency was replaced in August 1946, the total of all Hungarian banknotes in circulation equaled the value of one one-thousandth of a US Dollar.