Rule 2.5: Spelling and Pronunciation - The Present Progressive
C

s
r

V

i
u

C

t – sitting
n – running

In a one-syllable word, if the last three letters are a consonant-vowel-consonant combination (CVC), double the last consonant before adding -ing.
sew – sewing
fix – fixing
enjoy – enjoying
However, do not double the last consonant in words that end in w, x, or y.
admít – admitting
(the last syllable is stressed)

whísper – whispering
(the last syllable is not stressed, so you don’t double the -r.)

In words of two or more syllables that end in a consonant-vowel-consonant combination, double the last consonant only if the last syllable is stressed.