You can make 166 valid words from the letters in ILOPSTTY using the Scrabble US/CAN dictionary.
How many points is ILOPSTTY worth in Scrabble?
ILOPSTTY is worth 13 points in Scrabble (US/CAN) and 14 points in Words With Friends.
How do I use the Word Unscrambler tool?
Enter any letters into the input box and press Search. The tool will return every valid English word that can be made from those letters using the dictionary you select.