Expressing "exactly" with 恰好, 恰巧 and 刚好
The adverbs 刚好, 恰好 and 恰巧 have the same meaning, but differ slightly in usage.
The adverb 刚好
刚好 
is used to express that something happened in time.
It is placed either before a verb or a verb phrase.
is used to express that something happened in time.
It is placed either before a verb or a verb phrase.
Pay attention
刚好 is used in spoken language.
Examples
我要出门找他的时候他刚好回来了
He came back when I went out to look for him
wǒ yào chūmén zhǎo tā de shíhòu tā gānghǎo huíláile
我们刚好赶上那班公共汽车
We caught the bus in time
wǒmen gānghǎo gǎnshàng nà bān gōnggòng qìchē
我们刚好在演出结束前离开
We left just before the end of the show
wǒmen gānghǎo zài yǎnchū jiéshù qián líkāi
刚好 can also be used to emphasize quantity or size.
Examples
每个角都有1个警戒塔，每个塔刚好10米高
There is a 10-meter high watchtower at each corner
měi ge jiǎo dōu yǒu yí ge jǐngjiè tǎ, měi ge tǎ gānghǎo shí mǐ gāo
我这里刚好有一本小册子
I have just one booklet
wǒ zhèlǐ gānghǎo yǒu yì běn xiǎo cèzi
The adverb 恰好
恰好 is used to emphasize a fortunate coincidence.
It is placed either before a verb or a verb phrase.
is used to emphasize a fortunate coincidence.
It is placed either before a verb or a verb phrase. Pay attention
恰好 is used in written language.
Examples
这两车恰好能坐七个人
These two cars can seat seven people
zhè liǎng chē qiàhǎo néng zuò qī ge rén
我回家的路上恰好碰见了老师
I happened to bump into my teacher on my way home
wǒ huí jiā de lùshàng qiàhǎo pèngjiàn le lǎoshī
你需要的书我这里恰好有一本，你先拿去看吧
I happen to have one of the books you need. You can take it to read
nǐ xūyào de shū wǒ zhèlǐ qiàhǎo yǒu yì běn, nǐ xiān ná qù kàn ba
恰好 can also be used as part of a state complement.
Examples
你来得恰好
You are right on time
nǐ lái de qiàhǎo
你猜得恰好
You guessed it
nǐ cāi de qiàhǎo
The adverb 恰巧
恰巧 is similar to 恰好 and emphasizes either a fortunate coincidence or that something happened in time.
is similar to 恰好 and emphasizes either a fortunate coincidence or that something happened in time.Examples
平时我都不在家，今天恰巧没出门，你就来了
I'm usually not at home, but fortunately today I was here when you came by
píngshí wǒ dū bú zài jiā, jīntiān qiàqiǎo méi chūmén, nǐ jiù lái le
我正想叫辆出租车，恰巧一辆车就开过来了
I was about to call a taxi when a car pulled up
wǒ zhèng xiǎng jiào liàng chūzūchē, qiàqiǎo yí liàng chē jiù kāiguòlái le
恰巧 and 恰好 are used almost interchangeably.
Pay attention
恰好 cannot be used as part of a state complement.
Examples
你想找的这本书我恰巧有
I happen to have the book you're looking for
nǐ xiǎng zhǎo de zhè běn shū wǒ qiàqiǎo yǒu
你想找的这本书我恰好有
I happen to have the book you're looking for
nǐ xiǎng zhǎo de zhè běn shū wǒ qiàhǎo yǒu