Some historians estimate the number of magnates as 1% of the number of szlachta. Out of approx. one million szlachta, tens of thousands of families, only 200–300 persons could be classed as great magnates with country-wide possessions and influence, and 30–40 of them could be viewed as those with significant impact on Poland's politics.
Out of one million szlachtas how many were magnates? 
200–300