で言うと names the scale or the terms you are measuring by: "in terms of", "by", "as for". It goes straight after a noun.
、。
As for fruit, I like apples best.
、ごれいれい500。
In terms of calories, this cake is 500 kilocalories.
、。
By Japanese standards, this house is quite big.
、。
In terms of age, he is the oldest on the team.
means the same and can replace で言うと in any of these sentences.
Putting it another way
With a language, a unit or a familiar comparison, で言うと translates: it says the same thing in other terms. The question form asks for the equivalent.
、きごう？
What is it in Japanese?
、きごう？
What city would that be in Japan?
で言うと or と言えば
and
mean "speaking of": they pick up a topic and say what it brings to mind. で言うと sets up a scale and measures by it.
、。
Speaking of Kyoto, it is famous for its temples.
、。
In terms of price, this one is cheaper.
- × 京都で言えば、お寺が有名です → 京都と言えば、お寺が有名です
Lingaku