As a 副詞（ふくし） (adverb),
割（わり）に is usually used in a similar way to ‘although’, ‘despite’, or ‘comparatively’ in English.
割（わり）に may be used at the beginning of a sentence, or after any word/phrase that it is highlighting as being ‘comparative’. When following
な-Adjectives or nouns, な or の will be required.
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この肉（にく）、高（たか）い割（わり）には味（あじ）がないね。
Although this meat is expensive, it is not flavorful.
太（ふと）っている割（わり）には運動（うんどう）神経（しんけい）がいいんだね。
Although you are fat, you are very athletic, aren't you?
この機械（きかい）のパワーは強（つよ）い割（わり）にめちゃくちゃ遅（おそ）いです。
Although this machine is very powerful, it is very slow.
この部屋（へや）は綺麗（きれい）な割（わり）には臭（くさ）いね。
Although this room is clean, it smells bad.
ラッシュアワーの割（わり）には空（す）いていますね。
Although it is during rush hour, the road is very clear.
割（わり） itself is a 名詞（めいし） meaning ‘proportionate’, and is primarily used as a suffix.
割（わり）に may be thought of as a direct extension of this use, as ‘proportionately’ is its closest literal meaning.
While 割（わり）に is often thought to make comparisons between things, it actually only ever compares something to itself (or things within the same category). The ‘proportion’ that is then highlighted is something that is not common within the category of (A).
Both 割（わり）と and
割（わり）に are quite common expressions. However, 割（わり）と is used far more often in casual speech to show that something is ‘unexpectedly (A)’. It will also frequently be used as a stand-alone expression, appearing directly before the word (usually an adjective) that is of a ‘considerable’ amount.
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これ割（わり）と美味（あい）しいよ。
This is unexpectedly tasty.
昨日（きのう）買（か）った包丁（ほうちょう）は割（わり）といい。
The knife I bought yesterday is quite good.