Is there a rule why the correct spelling for "Marketing" is not " Marketting"? [duplicate]
"In a one-syllable verb ending in one consonant letter preceded by one vowel letter, double the final consonant letter (never double "w, x, y")."
It's the syllable that matters, not the length of a word, although most of the time these two are well related.
See more at: Doubling the Final Consonant in a Verb