One of the commonest questions asked about Stonehenge:
There are 92 rocks at Stonehenge now - See http://www.sarsen.org/2012/11/91-total-number-of-visible-stones-at.html for details. The rocks are counted differently to the number of stones. A broken stone is counted as two rocks if it has two separate pieces visible.
How many stones did Stonehenge originally have is a different question.
There are five Sarsen Trilithons which gives fifteen large Sarsen stones.
The outer ring of Sarsens is planned to contain thirty uprights and thirty lintels so that is 75 worked sarsens in total.
There are four sarsens outside the centre, the two Station Stones, the Slaughter Stone and the Heel Stone.
There are stoneholes for other stones matching these, another two station stones, a matching Slaughter Stone and a paired hole to the Heel Stone. (There are other holes such as the F,G and H holes which maybe were stoneholes.) These empty holes may have held other stones or maybe stones that were then moved, for instance the Heel Stone may have originally occupied Stonehole 97. So that is between five and ten other sarsens.
There is the Altar Stone, origin unknown.
And lots of bluestones and bluestone holes. There are 29 bluestones that are still visible, but the original number is probably around 80. They have been shuffled around the holes so it is hard to be sure but that is a reasonable estimate.
So Stonehenge may have had up to 165 stones originally. It also had a vast number of stone fragments and hammerstones used for packing.
Where are the missing stones from Stonehenge?
We don't know.
There is broken up bluestone, known as debitage, all over the site. Is this from stones being broken up for tools and talismen or is it the remains of shaping the stones?
We know bits have been knocked off the edges of stones, greatly reducing them in some cases but complete stones carted off for use elsewhere have not been found despite searches. So it is another Stonehenge mystery.