"How many Templarts were there? This is one of those questions that people interested in the Templars often ask. But so far as we know the Templars did not keep membership lists; certainly none have survived. (...) it appears that there were around 300 Templar knights in the kingdom of Jerusalem in the 1180s. Malcolm Barber has estimated that there were around 1,000 sergeant-brothers in addition to the 300 knight-brothers.
Is this a reasonable figure? (...) the estimated figure of 1,300 Templars in the East in the 1180s is too large. Perhaps there were only 300 brothers in total, in the whole of the East; that would mean that numbers more than halved between the 1180s and the early fourteenth century, but that would be reasonable after the losses of 1291-1302.
That is only the East: how many Templars were there overall? ... so far this suggests that there were no more than 1,500 Templars in Europe and Cyprus in 1307."
Text and illustration from the blog by "Gawain's Mum" on gawainsmum.wordpress.com. Illustration shows Four Templar knights on the tomb of Don Felipe in the former Templar church of Santa Maria la Blanca de Villasirga, at Villacazar de irga (Palencia, Castile, Spain). Photo: Juan Fuguet Sans