Count each vowel in a word. Vowels include the letters a, e, i, o, u and sometimes y.
Subtract one from your total number of vowels for silent vowels such as the "e" in the word "move."
Subtract one from your total number of vowels for double vowels that have one sound, such as the double a in the name "Aaron." Another example is the double o letters in the word "pool." Only count one syllable for the two vowels together.
Subtract one from your number of vowels for each diphthong, a combination of vowels that make one sound. For instance, in the word "out" there are two vowels working together to make one sound. Therefore, subtract one from the total number of vowels in this word.
Equate your final answer with the number of syllables in the word. For example, in the word "astronaut" there are four vowels - a, o, a and u. The vowels a and u together are a diphthong, so you would subtract 1 from 4 to get a total of 3 syllables for this word.