から言(い)うとSpeaking in terms of, From the point of view of

からいうと (appearing with or without kanji) is a phrase in Japanese that is used to express a particular viewpoint or standpoint from which some type of evaluation, conclusion, or opinion can be drawn. The と that appears here is one of the assumption uses of this particle, meaning that から言(い)えば may also be used.

からいうと will always follow a noun (or noun phrase), before the (B) part of that same sentence will describe some kind of evaluation/opinion/etc. This structure closely reflects phrases like 'speaking in terms of (A), (B)', or 'what can be drawn from (A) is that (B)'.

Occasonally, the use of particles such as と or ば may be skipped entirely, with から言(い)って being used instead.

Caution

'Name + からいうと' may not be used with this expression, as a person is not a 'situation'. However, it is perfectly ok to use something like 'name の 立場(たちば)からいうと', as this highlights a specific situation that the said person is in.

Caution

Due to からいうと regularly highlighting some sort of 'overall situation', it will not be used with momentary/visual things. In these cases, while not strictly incorrect, it may sound quite unnatural to a native speaker.

A more appropriate choice here would be something like から見(み)ると, as this can be used to make purely visual assessments.