You can make 158 valid words from the letters in EFIRSST using the Scrabble US/CAN dictionary.
How many points is EFIRSST worth in Scrabble?
EFIRSST is worth 10 points in Scrabble (US/CAN) and 10 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.