temporalhopr:

Frisks age is a widely debated topic in the Undertale community. It’s never really specifically stated so it can be hard to get definitive info on it. However I believe I’ve found a proper conclusion to this debate.

Frisks Physical Features

One thing that can help us define Frisks age is there physical features. They are a short person who’s somewhat chubby. 

These things are characteristics of a young child. Their canon height is very short as well, being even shorter than Sans. 

All of Frisks canon artwork/concept art also depicts them being incredibly short. 

They’re even shown to be as small as Papyrus’ boots. 

This also seems to imply a decently young age based off of height and physical appearance alone. However we also have to take some other factors into account, such as their characteristics.

Frisks Characteristics 

While height and physical appearance added to our proof there’s still their characteristics that need to be discussed. Frisk is constantly referred to in a childlike manner. Chara sings them a nursery rhyme,

which would be strange if they weren’t decently young. Chara also calls them cute (No this isn’t a ship post, shoo charisk shippers).

But not only does Chara refer to them as if they were a young child but the other characters do as well. Characters constantly call them “child” or “kid”. 

Undyne even says that she isn’t “Frisks kindergarten teacher”. 

With all this in mind I think it’s safe to say that Frisk is a young child somewhere between 6-8 years old. 

TL;DR

In conclusion Frisk is likely somewhere between 6-8 years old based off of their physical appearance and childlike characteristics.