That's difficult to determine because there are so many small Grand Lodges. Some of them are all male, others all female, and some mixed. The best estimate I've come across is around 250,000, but that may not be entirely accurate. The problem arises that the
Modern Grand Lodges/Orients tend to be quite liberal and allow the lodges to choose their own rituals. Some of these lodges choose
Antient or Emmulation rituals.
From the Grand Lodge perspective we could say 250,000, but at the local lodge level no one has a clue. I would venture a guess that there are probably around 125,000 Masons practicing true 'Modern' rituals, as put forth by the Grand Lodge of London in 1717. That, however, is just a guess.
Jeff