How Many Days Should I Allot To Visit Angkor What?

The Angkor Archaeological Park has five main groups of wats, spread out over 25 square miles. Angkor proper is 3 miles from Siem Riep. You should spend at least three days touring the ruins.
Purchase passes on the main road to Angkor Wat for one-, three- or seven-day blocks, priced at $20, $4 and $60, respectively. Note: You must have a passport photo to laminate onto your entry pass -- or stand in a long line to have a photo taken. The pass allows you access to the main complexes and most of the outlying temples.
Our plane from Bangkok arrived in mid-afternoon. We rented bicycles from our guesthouse and went to Angkor Wat (the closest temple), staying long enough for the fabled sunset over the buildings.
Next day, we were back on the bikes for a 25-mile  loop to Angkor Thom, the Bayon Group, the West Baray sites, and Preah Khan, Neak Prean and Ta Son to the north of Thom.
Seeing the ruins by bike was especially fun because after you leave the main circuits, the jungle gives way to rice paddies, and you are in rural, old-style Cambodia: women in traditional dress, naked boys swimming in irrigation ditches, families interacting in plank or woven-reed homes, barnyard animals.
Next day, we hired a "tuk-tuk" (motorcycle taxi) to take us to Banteay Srei and the Roulos Group of temples, both about 12 miles from Siem Riep in different directions. The day ended with a look at Tonle Sap Lake.
So, we saw most of the temples in a leisurely three and a half days.