正好 (just right / exactly)

Perfect timing

• You are about to phone your friend when your phone rings — it's her.
• you你nǐto emerge (from a…来得lái dejust right正好zhèng hǎo，I我wǒ正想zhèng xiǎngto / for / give给gěiyou你nǐto make a telephone call打电话dǎ diàn huà。 — "You've come at just the right moment; I was just about to call you."

just right正好zhèng hǎo = just right

• As a description: size大小dà xiǎojust right正好zhèng hǎo。 — "The size is just right." (concept of) time时间shí jiānjust right正好zhèng hǎo — "The timing is perfect."
• After a (degree marker)得de complement: you你nǐto emerge (from a…来得lái dejust right正好zhèng hǎo — "You came at the right time."

this这zhèpair of双shuāngshoes鞋xiésize大小dà xiǎojust right正好zhèng hǎo。

just right正好zhèng hǎo + Verb = happen to

• I我wǒjust right正好zhèng hǎoalso也yěbe going to要yàogo to去qùthe supermarket超市chāo shì，in the same place一起yì qǐto walk走zǒu(suggestion)吧ba。 — "I happen to be going to the supermarket too; let's go together."
• It points to a lucky coincidence that fits the situation.

I我wǒhappen to正好zhèng hǎoalso也yěbe going to要yàogo to去qùthe supermarket超市chāo shì。

Exactly an amount

just right正好zhèng hǎo versus just刚好gāng hǎo and in the middle of正在zhèng zài

• just刚好gāng hǎo is almost the same as just right正好zhèng hǎo: just刚好gāng hǎo十点shí diǎn.
• just right正好zhèng hǎo can also open a sentence to stress the lucky timing: just right正好zhèng hǎo，he / him他tāalso也yěat / in在zàithere那儿nà ér — "As it happened, he was there too."

in total一共yí gòngexactly正好zhèng hǎoone hundred一百yì bǎiyuan块kuài。

Recap

Read the full reference: HSK 4 grammar — Adverbs.