Tip: See my list of the Most Common Mistakes in English. It will teach you how to avoid mis­takes with com­mas, pre­pos­i­tions, ir­reg­u­lar verbs, and much more.

As you surely know, the final consonant of some verbs gets doubled when the suffix -ing or -ed is added, e.g.

stop: sto pp ing, sto pp ed

cram: cra mm ing, cra mm ed

In other cases, it is not doubled:

visit: visi t ing, visi t ed

shift: shif t ing, shif t ed

The rule governing the doubling of the final consonant is actually quite simple. If a verb has just one syllable and ends with exactly one vowel followed by one consonant (except “w”, “x”, and “y”, which we will explain below), the consonant is doubled:

rob: ro bb ing, ro bb ed

sit: si tt ing, (past tense: sat)

beg: be gg ing, be gg ed

hum: hu mm ing, hu mm ed

If there are two vowels or two consonants at the end, no doubling occurs:

r ea d: rea d ing, (past tense: read)

c oa t: coa t ing, coa t ed

ba rk : bar k ing, bar k ed

fi ll : fil l ing, fil l ed

This applies also to “oo” and “ee”:

c oo k: coo k ing, coo k ed

s ee d: see d ing, see d ed

Similarly, if a verb ends with a silent “e”, do not double the preceding consonant:

tak e : ta k ing, (past tense: took)

com e : co m ing, (past tense: came)

hop e : ho p ing, ho p ed

gam e : ga m ing, ga m ed

The letters “w” and “y” are never doubled (they act as vowels in this context, pronounced /ʊ/ and /ɪ/, respectively):

sno w : sno w ing, sno w ed

sta y : sta y ing, sta y ed

Similarly, the letter “x” is never doubled, because it represents two consonants “ks”:

bo x : bo x ing, bo x ed

ve x : ve x ing, ve x ed

Words beginning with “qu” may seem like an exception to the rule, but “qu” is actually pronounced as “kw”, i.e. as two consonants, which does not prevent the following vowel from doubling:

quiz: qui zz ing, qui zz ed (think of “kwiz”)

quit: qui tt ing (past tense is usually just “quit”)

The rule can be summarized as:

One vowel + one consonant ⇒ doubling

(in monosyllabic words; except -w, -x, -y)

How does the rule apply to polysyllabic words? I will describe all the details in another article. In the meantime, you can check out my book, which describes all the rules and exceptions.