Its my theory

Frisk=12

Chara=15

Asriel=15

Flowey=IMMORTAL

Toriel=38

Asgore=46

Napstablook=100000000000

Sans=25

Papyrus=20

Undyne=23

Alphys=22

Grillby's=32

Monster kids=9-12

Mettaton=5

Wd.Gaster= ✋︎ 👎︎⚐︎☠︎❄︎ 😐︎☠︎⚐︎🕈︎

✋︎❄︎💧︎ ☺︎🕆︎💧︎❄︎ 💣︎✋︎💧︎❄︎☜︎☼︎✡︎

💣︎ ✋︎ 💧︎ ❄︎ ☜︎ ☼︎ ✡︎

Nice Ceam guy=23

Burgerpants=19

Muffet=20

Bratty and catty=25-29

Temmie=TEM

Asriel (god of hyperdeath)=19

Yeah that my theory

Here is my prediction:

Frisk: 11

Chara: 12

Sans: 25

Papyrus: 20

Toriel: 30

Asgore: 40

Undyne: 18

Alphys: 20

Asriel: 12

Uhhh maybe alphys is slightly younger than undyne???

Sorry Frans shippers but frisk was never confirmed 16 and sans was never confirmed 18, if sans was 18 and frisk was 16 he wouldn't call them kiddo, its just a myth that frans shippers throw around to make up for frisk being implied to be a kid. If you have proof that frisk is 16 and sans is 18 than show it to me.

Not hating on frans or anything, its just frisk is not 16.

Here's there age

Sans-21

Papyrus-13

Alphys- 23-27

Undyne-12

Toriel-29

Asgore-37-38

Asriel-7

Flowey- Flower

Frisk5-8

Chara-20-30

Muffet-20

That's all of the one's I know the age of...

I'd say Frisk is 13-18, Sans is 18-25, Papyrus is 16-20, undyne is 17-24, and Alphys will be 16-22, Asgore and Toriel both 30+

Frisk is 100% not 16!!! I think Frisk is 5 since undertale was made in 2015

I think Asgore is about 800-1200 years old; and Toriel is most likely younger; at 700-900; Chara is about 12-13, probably because most young kids don't know what suicide is. Frisk should be 8-11, and Asriel (excluding flowey years) is about 10-12. Asriel (including flowey years) is thousands of years old. Mettaton should be about 100-120 years old, with Napstablook being in the same range. For Sans and Papyrus, Papyrus is confirmed to be 17 by a neutral ending where he turns 18; and Sans should be 10-15 years older. (so fontcest shippers are also putting non-socially acceptable age gaps. SCREW YOU IDIOTS-) Alphys is somewhere over 18 because she has her job, but younger than 40. Undyne is about 20-24. All characters with JOBS are over 18, please keep that in mind, (also please don't ship characters that have awfully large age gaps.) A message from your friend, MuradisDaBeast (also, PLEASE TRY TO FIX THE UNDERTALE FANDOM BECAUSE THERE IS ALOT OF RULE 34 TRASH; DONT SEARCH UP WHATEVER THAT IS-)

@UndertaleFriskTheHuman Then every other character in the game is also 5 , so no.

@MuradisDaBeast Wait papyrus is 17?? What neutral ending was it.